[{"_id":"9407","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","date_updated":"2026-04-03T09:37:18Z","year":"2021","month":"05","publication_identifier":{"eissn":["2041-1723"]},"volume":12,"ddc":["570"],"type":"journal_article","citation":{"ieee":"D. Scarselli, N. B. Budanur, M. Timme, and B. Hof, “Discontinuous epidemic transition due to limited testing,” <i>Nature Communications</i>, vol. 12, no. 1. Springer Nature, 2021.","mla":"Scarselli, Davide, et al. “Discontinuous Epidemic Transition Due to Limited Testing.” <i>Nature Communications</i>, vol. 12, no. 1, 2586, Springer Nature, 2021, doi:<a href=\"https://doi.org/10.1038/s41467-021-22725-9\">10.1038/s41467-021-22725-9</a>.","chicago":"Scarselli, Davide, Nazmi B Budanur, Marc Timme, and Björn Hof. “Discontinuous Epidemic Transition Due to Limited Testing.” <i>Nature Communications</i>. Springer Nature, 2021. <a href=\"https://doi.org/10.1038/s41467-021-22725-9\">https://doi.org/10.1038/s41467-021-22725-9</a>.","ama":"Scarselli D, Budanur NB, Timme M, Hof B. Discontinuous epidemic transition due to limited testing. <i>Nature Communications</i>. 2021;12(1). doi:<a href=\"https://doi.org/10.1038/s41467-021-22725-9\">10.1038/s41467-021-22725-9</a>","short":"D. Scarselli, N.B. Budanur, M. Timme, B. Hof, Nature Communications 12 (2021).","apa":"Scarselli, D., Budanur, N. B., Timme, M., &#38; Hof, B. (2021). Discontinuous epidemic transition due to limited testing. <i>Nature Communications</i>. Springer Nature. <a href=\"https://doi.org/10.1038/s41467-021-22725-9\">https://doi.org/10.1038/s41467-021-22725-9</a>","ista":"Scarselli D, Budanur NB, Timme M, Hof B. 2021. Discontinuous epidemic transition due to limited testing. Nature Communications. 12(1), 2586."},"quality_controlled":"1","language":[{"iso":"eng"}],"publication":"Nature Communications","acknowledgement":"The authors thank Malte Schröder for valuable discussions and creating the scale-free network topologies. B.H. thanks Mukund Vasudevan for helpful discussion. The research by M.T. was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany´s Excellence Strategy–EXC-2068–390729961–Cluster of Excellence Physics of Life of TU Dresden.","intvolume":"        12","doi":"10.1038/s41467-021-22725-9","date_published":"2021-05-10T00:00:00Z","article_number":"2586","day":"10","status":"public","has_accepted_license":"1","scopus_import":"1","oa":1,"tmp":{"short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"author":[{"last_name":"Scarselli","first_name":"Davide","id":"40315C30-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0001-5227-4271","full_name":"Scarselli, Davide"},{"last_name":"Budanur","first_name":"Nazmi B","id":"3EA1010E-F248-11E8-B48F-1D18A9856A87","full_name":"Budanur, Nazmi B","orcid":"0000-0003-0423-5010"},{"last_name":"Timme","first_name":"Marc","full_name":"Timme, Marc"},{"last_name":"Hof","id":"3A374330-F248-11E8-B48F-1D18A9856A87","first_name":"Björn","full_name":"Hof, Björn","orcid":"0000-0003-2057-2754"}],"department":[{"_id":"BjHo"}],"publisher":"Springer Nature","isi":1,"file":[{"creator":"kschuh","relation":"main_file","file_name":"2021_NatureCommunications_Scarselli.pdf","content_type":"application/pdf","success":1,"date_created":"2021-05-25T14:18:40Z","access_level":"open_access","checksum":"fe26c1b8a7da1ae07a6c03f80ff06ea1","date_updated":"2021-05-25T14:18:40Z","file_id":"9426","file_size":1176573}],"pmid":1,"external_id":{"pmid":["33972522"],"isi":["000687305500044"]},"abstract":[{"text":"High impact epidemics constitute one of the largest threats humanity is facing in the 21st century. In the absence of pharmaceutical interventions, physical distancing together with testing, contact tracing and quarantining are crucial in slowing down epidemic dynamics. Yet, here we show that if testing capacities are limited, containment may fail dramatically because such combined countermeasures drastically change the rules of the epidemic transition: Instead of continuous, the response to countermeasures becomes discontinuous. Rather than following the conventional exponential growth, the outbreak that is initially strongly suppressed eventually accelerates and scales faster than exponential during an explosive growth period. As a consequence, containment measures either suffice to stop the outbreak at low total case numbers or fail catastrophically if marginally too weak, thus implying large uncertainties in reliably estimating overall epidemic dynamics, both during initial phases and during second wave scenarios.","lang":"eng"}],"file_date_updated":"2021-05-25T14:18:40Z","article_type":"original","issue":"1","related_material":{"link":[{"relation":"press_release","description":"News on IST Homepage","url":"https://ist.ac.at/en/news/smashing-the-covid-curve/"}]},"date_created":"2021-05-23T22:01:42Z","publication_status":"published","oa_version":"Published Version","title":"Discontinuous epidemic transition due to limited testing","article_processing_charge":"No"},{"month":"07","publication_identifier":{"issn":["0022-1120"],"eissn":["1469-7645"]},"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","_id":"9467","date_updated":"2025-07-10T12:01:47Z","year":"2021","doi":"10.1017/jfm.2021.371","article_number":"A17","date_published":"2021-07-25T00:00:00Z","day":"25","ddc":["530"],"volume":919,"citation":{"ieee":"E. Marensi, S. He, and A. P. Willis, “Suppression of turbulence and travelling waves in a vertical heated pipe,” <i>Journal of Fluid Mechanics</i>, vol. 919. Cambridge University Press, 2021.","chicago":"Marensi, Elena, Shuisheng He, and Ashley P. Willis. “Suppression of Turbulence and Travelling Waves in a Vertical Heated Pipe.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2021. <a href=\"https://doi.org/10.1017/jfm.2021.371\">https://doi.org/10.1017/jfm.2021.371</a>.","mla":"Marensi, Elena, et al. “Suppression of Turbulence and Travelling Waves in a Vertical Heated Pipe.” <i>Journal of Fluid Mechanics</i>, vol. 919, A17, Cambridge University Press, 2021, doi:<a href=\"https://doi.org/10.1017/jfm.2021.371\">10.1017/jfm.2021.371</a>.","short":"E. Marensi, S. He, A.P. Willis, Journal of Fluid Mechanics 919 (2021).","ama":"Marensi E, He S, Willis AP. Suppression of turbulence and travelling waves in a vertical heated pipe. <i>Journal of Fluid Mechanics</i>. 2021;919. doi:<a href=\"https://doi.org/10.1017/jfm.2021.371\">10.1017/jfm.2021.371</a>","apa":"Marensi, E., He, S., &#38; Willis, A. P. (2021). Suppression of turbulence and travelling waves in a vertical heated pipe. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2021.371\">https://doi.org/10.1017/jfm.2021.371</a>","ista":"Marensi E, He S, Willis AP. 2021. Suppression of turbulence and travelling waves in a vertical heated pipe. Journal of Fluid Mechanics. 919, A17."},"type":"journal_article","language":[{"iso":"eng"}],"quality_controlled":"1","intvolume":"       919","publication":"Journal of Fluid Mechanics","acknowledgement":"The anonymous referees are kindly acknowledged for their useful suggestions andcomments.","author":[{"first_name":"Elena","id":"0BE7553A-1004-11EA-B805-18983DDC885E","last_name":"Marensi","orcid":"0000-0001-7173-4923","full_name":"Marensi, Elena"},{"last_name":"He","first_name":"Shuisheng","full_name":"He, Shuisheng"},{"last_name":"Willis","first_name":"Ashley P.","full_name":"Willis, Ashley P."}],"corr_author":"1","publisher":"Cambridge University Press","department":[{"_id":"BjHo"}],"isi":1,"status":"public","has_accepted_license":"1","oa":1,"scopus_import":"1","tmp":{"short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"oa_version":"Published Version","date_created":"2021-06-06T22:01:30Z","publication_status":"published","title":"Suppression of turbulence and travelling waves in a vertical heated pipe","article_processing_charge":"Yes (via OA deal)","arxiv":1,"file":[{"date_updated":"2021-08-03T09:53:28Z","file_size":4087358,"file_id":"9766","creator":"kschuh","content_type":"application/pdf","relation":"main_file","file_name":"2021_JournalFluidMechanics_Marensi.pdf","checksum":"867ad077e45c181c2c5ec1311ba27c41","date_created":"2021-08-03T09:53:28Z","success":1,"access_level":"open_access"}],"external_id":{"arxiv":["2008.13486"],"isi":["000653785000001"]},"abstract":[{"text":"Turbulence in the flow of fluid through a pipe can be suppressed by buoyancy forces. As the suppression of turbulence leads to severe heat transfer deterioration, this is an important and undesirable phenomenon in both heating and cooling applications. Vertical flow is often considered, as the axial buoyancy force can help drive the flow. With heating measured by the buoyancy parameter 𝐶, our direct numerical simulations show that shear-driven turbulence may either be completely laminarised or it transitions to a relatively quiescent convection-driven state. Buoyancy forces cause a flattening of the base flow profile, which in isothermal pipe flow has recently been linked to complete suppression of turbulence (Kühnen et al., Nat. Phys., vol. 14, 2018, pp. 386–390), and the flattened laminar base profile has enhanced nonlinear stability (Marensi et al., J. Fluid Mech., vol. 863, 2019, pp. 50–875). In agreement with these findings, the nonlinear lower-branch travelling-wave solution analysed here, which is believed to mediate transition to turbulence in isothermal pipe flow, is shown to be suppressed by buoyancy. A linear instability of the laminar base flow is responsible for the appearance of the relatively quiescent convection driven state for 𝐶≳4 across the range of Reynolds numbers considered. In the suppression of turbulence, however, i.e. in the transition from turbulence, we find clearer association with the analysis of He et al. (J. Fluid Mech., vol. 809, 2016, pp. 31–71) than with the above dynamical systems approach, which describes better the transition to turbulence. The laminarisation criterion He et al. propose, based on an apparent Reynolds number of the flow as measured by its driving pressure gradient, is found to capture the critical 𝐶=𝐶𝑐𝑟(𝑅𝑒) above which the flow will be laminarised or switch to the convection-driven type. Our analysis suggests that it is the weakened rolls, rather than the streaks, which appear to be critical for laminarisation.","lang":"eng"}],"article_type":"original","file_date_updated":"2021-08-03T09:53:28Z"},{"date_updated":"2026-04-07T11:47:05Z","_id":"9558","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","year":"2021","acknowledged_ssus":[{"_id":"ScienComp"}],"month":"06","publication_identifier":{"eissn":["1079-7114"],"issn":["0031-9007"]},"citation":{"ista":"Yalniz G, Hof B, Budanur NB. 2021. Coarse graining the state space of a turbulent flow using periodic orbits. Physical Review Letters. 126(24), 244502.","apa":"Yalniz, G., Hof, B., &#38; Budanur, N. B. (2021). Coarse graining the state space of a turbulent flow using periodic orbits. <i>Physical Review Letters</i>. American Physical Society. <a href=\"https://doi.org/10.1103/PhysRevLett.126.244502\">https://doi.org/10.1103/PhysRevLett.126.244502</a>","mla":"Yalniz, Gökhan, et al. “Coarse Graining the State Space of a Turbulent Flow Using Periodic Orbits.” <i>Physical Review Letters</i>, vol. 126, no. 24, 244502, American Physical Society, 2021, doi:<a href=\"https://doi.org/10.1103/PhysRevLett.126.244502\">10.1103/PhysRevLett.126.244502</a>.","chicago":"Yalniz, Gökhan, Björn Hof, and Nazmi B Budanur. “Coarse Graining the State Space of a Turbulent Flow Using Periodic Orbits.” <i>Physical Review Letters</i>. American Physical Society, 2021. <a href=\"https://doi.org/10.1103/PhysRevLett.126.244502\">https://doi.org/10.1103/PhysRevLett.126.244502</a>.","short":"G. Yalniz, B. Hof, N.B. Budanur, Physical Review Letters 126 (2021).","ama":"Yalniz G, Hof B, Budanur NB. Coarse graining the state space of a turbulent flow using periodic orbits. <i>Physical Review Letters</i>. 2021;126(24). doi:<a href=\"https://doi.org/10.1103/PhysRevLett.126.244502\">10.1103/PhysRevLett.126.244502</a>","ieee":"G. Yalniz, B. Hof, and N. B. Budanur, “Coarse graining the state space of a turbulent flow using periodic orbits,” <i>Physical Review Letters</i>, vol. 126, no. 24. American Physical Society, 2021."},"type":"journal_article","volume":126,"publication":"Physical Review Letters","acknowledgement":"We thank the referees for improving this Letter with their comments. We acknowledge stimulating discussions with\r\nH. Edelsbrunner. This work was supported by Grant No. 662960 from the Simons Foundation (B. H.). The numerical calculations were performed at TUBITAK ULAKBIM High Performance and Grid Computing Center (TRUBA resources) and IST Austria High Performance Computing cluster.","intvolume":"       126","quality_controlled":"1","language":[{"iso":"eng"}],"doi":"10.1103/PhysRevLett.126.244502","day":"18","main_file_link":[{"url":"https://arxiv.org/abs/2007.02584","open_access":"1"}],"article_number":"244502","date_published":"2021-06-18T00:00:00Z","status":"public","scopus_import":"1","oa":1,"corr_author":"1","author":[{"last_name":"Yalniz","id":"66E74FA2-D8BF-11E9-8249-8DE2E5697425","first_name":"Gökhan","full_name":"Yalniz, Gökhan","orcid":"0000-0002-8490-9312"},{"full_name":"Hof, Björn","orcid":"0000-0003-2057-2754","last_name":"Hof","first_name":"Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87"},{"full_name":"Budanur, Nazmi B","orcid":"0000-0003-0423-5010","last_name":"Budanur","first_name":"Nazmi B","id":"3EA1010E-F248-11E8-B48F-1D18A9856A87"}],"project":[{"_id":"238598C6-32DE-11EA-91FC-C7463DDC885E","name":"Revisiting the Turbulence Problem Using Statistical Mechanics","grant_number":"662960"}],"isi":1,"department":[{"_id":"GradSch"},{"_id":"BjHo"}],"publisher":"American Physical Society","abstract":[{"text":"We show that turbulent dynamics that arise in simulations of the three-dimensional Navier--Stokes equations in a triply-periodic domain under sinusoidal forcing can be described as transient visits to the neighborhoods of unstable time-periodic solutions. Based on this description, we reduce the original system with more than 10^5 degrees of freedom to a 17-node Markov chain where each node corresponds to the neighborhood of a periodic orbit. The model accurately reproduces long-term averages of the system's observables as weighted sums over the periodic orbits.\r\n","lang":"eng"}],"external_id":{"arxiv":["2007.02584"],"isi":["000663310100008"]},"article_type":"letter_note","issue":"24","arxiv":1,"article_processing_charge":"No","title":"Coarse graining the state space of a turbulent flow using periodic orbits","oa_version":"Preprint","date_created":"2021-06-16T15:45:36Z","related_material":{"record":[{"id":"19591","status":"returned","relation":"popular_science"},{"relation":"dissertation_contains","status":"public","id":"19684"}],"link":[{"url":"https://ist.ac.at/en/news/turbulent-flow-simplified/","description":"News on IST Homepage","relation":"press_release"}]},"publication_status":"published"},{"publication_identifier":{"issn":["2663-337X"]},"month":"07","acknowledged_ssus":[{"_id":"M-Shop"}],"year":"2021","OA_place":"publisher","_id":"9728","supervisor":[{"id":"3A374330-F248-11E8-B48F-1D18A9856A87","first_name":"Björn","last_name":"Hof","orcid":"0000-0003-2057-2754","full_name":"Hof, Björn"}],"user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","date_updated":"2026-04-16T08:43:20Z","date_published":"2021-07-29T00:00:00Z","day":"29","doi":"10.15479/at:ista:9728","language":[{"iso":"eng"}],"ddc":["532"],"type":"dissertation","citation":{"ista":"Agrawal N. 2021. Transition to turbulence and drag reduction in particle-laden pipe flows. Institute of Science and Technology Austria.","apa":"Agrawal, N. (2021). <i>Transition to turbulence and drag reduction in particle-laden pipe flows</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:9728\">https://doi.org/10.15479/at:ista:9728</a>","ama":"Agrawal N. Transition to turbulence and drag reduction in particle-laden pipe flows. 2021. doi:<a href=\"https://doi.org/10.15479/at:ista:9728\">10.15479/at:ista:9728</a>","short":"N. Agrawal, Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows, Institute of Science and Technology Austria, 2021.","mla":"Agrawal, Nishchal. <i>Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows</i>. Institute of Science and Technology Austria, 2021, doi:<a href=\"https://doi.org/10.15479/at:ista:9728\">10.15479/at:ista:9728</a>.","chicago":"Agrawal, Nishchal. “Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.” Institute of Science and Technology Austria, 2021. <a href=\"https://doi.org/10.15479/at:ista:9728\">https://doi.org/10.15479/at:ista:9728</a>.","ieee":"N. Agrawal, “Transition to turbulence and drag reduction in particle-laden pipe flows,” Institute of Science and Technology Austria, 2021."},"publisher":"Institute of Science and Technology Austria","department":[{"_id":"GradSch"},{"_id":"BjHo"}],"author":[{"full_name":"Agrawal, Nishchal","last_name":"Agrawal","first_name":"Nishchal","id":"469E6004-F248-11E8-B48F-1D18A9856A87"}],"corr_author":"1","alternative_title":["ISTA Thesis"],"oa":1,"tmp":{"short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"has_accepted_license":"1","status":"public","date_created":"2021-07-27T13:40:30Z","publication_status":"published","oa_version":"Published Version","related_material":{"record":[{"relation":"part_of_dissertation","status":"public","id":"6189"}]},"title":"Transition to turbulence and drag reduction in particle-laden pipe flows","article_processing_charge":"No","keyword":["Drag Reduction","Transition to Turbulence","Multiphase Flows","particle Laden Flows","Complex Flows","Experiments","Fluid Dynamics"],"degree_awarded":"PhD","file_date_updated":"2022-07-29T22:30:05Z","file":[{"content_type":"application/x-zip-compressed","relation":"source_file","file_name":"Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.zip","creator":"nagrawal","access_level":"closed","embargo_to":"open_access","date_created":"2021-07-28T13:32:02Z","checksum":"77436be3563a90435024307b1b5ee7e8","date_updated":"2022-07-29T22:30:05Z","file_id":"9744","file_size":22859658},{"date_updated":"2022-07-29T22:30:05Z","file_id":"9745","file_size":18658048,"embargo":"2022-07-28","file_name":"Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.pdf","content_type":"application/pdf","relation":"main_file","creator":"nagrawal","access_level":"open_access","date_created":"2021-07-28T13:32:05Z","checksum":"72a891d7daba85445c29b868c22575ed"}],"page":"118","abstract":[{"lang":"eng","text":"Most real-world flows are multiphase, yet we know little about them compared to their single-phase counterparts. Multiphase flows are more difficult to investigate as their dynamics occur in large parameter space and involve complex phenomena such as preferential concentration, turbulence modulation, non-Newtonian rheology, etc. Over the last few decades, experiments in particle-laden flows have taken a back seat in favour of ever-improving computational resources. However, computers are still not powerful enough to simulate a real-world fluid with millions of finite-size particles. Experiments are essential not only because they offer a reliable way to investigate real-world multiphase flows but also because they serve to validate numerical studies and steer the research in a relevant direction. In this work, we have experimentally investigated particle-laden flows in pipes, and in particular, examined the effect of particles on the laminar-turbulent transition and the drag scaling in turbulent flows.\r\n\r\nFor particle-laden pipe flows, an earlier study [Matas et al., 2003] reported how the sub-critical (i.e., hysteretic) transition that occurs via localised turbulent structures called puffs is affected by the addition of particles. In this study, in addition to this known transition, we found a super-critical transition to a globally fluctuating state with increasing particle concentration. At the same time, the Newtonian-type transition via puffs is delayed to larger Reynolds numbers. At an even higher concentration, only the globally fluctuating state is found. The dynamics of particle-laden flows are hence determined by two competing instabilities that give rise to three flow regimes: Newtonian-type turbulence at low, a particle-induced globally fluctuating state at high, and a coexistence state at intermediate concentrations.\r\n\r\nThe effect of particles on turbulent drag is ambiguous, with studies reporting drag reduction, no net change, and even drag increase. The ambiguity arises because, in addition to particle concentration, particle shape, size, and density also affect the net drag. Even similar particles might affect the flow dissimilarly in different Reynolds number and concentration ranges. In the present study, we explored a wide range of both Reynolds number and concentration, using spherical as well as cylindrical particles. We found that the spherical particles do not reduce drag while the cylindrical particles are drag-reducing within a specific Reynolds number interval. The interval strongly depends on the particle concentration and the relative size of the pipe and particles. Within this interval, the magnitude of drag reduction reaches a maximum. These drag reduction maxima appear to fall onto a distinct power-law curve irrespective of the pipe diameter and particle concentration, and this curve can be considered as the maximum drag reduction asymptote for a given fibre shape. Such an asymptote is well known for polymeric flows but had not been identified for particle-laden flows prior to this work."}]},{"type":"journal_article","citation":{"chicago":"Choueiri, George H, Jose M Lopez Alonso, Atul Varshney, Sarath Sankar, and Björn Hof. “Experimental Observation of the Origin and Structure of Elastoinertial Turbulence.” <i>Proceedings of the National Academy of Sciences of the United States of America</i>. National Academy of Sciences, 2021. <a href=\"https://doi.org/10.1073/pnas.2102350118\">https://doi.org/10.1073/pnas.2102350118</a>.","mla":"Choueiri, George H., et al. “Experimental Observation of the Origin and Structure of Elastoinertial Turbulence.” <i>Proceedings of the National Academy of Sciences of the United States of America</i>, vol. 118, no. 45, e2102350118, National Academy of Sciences, 2021, doi:<a href=\"https://doi.org/10.1073/pnas.2102350118\">10.1073/pnas.2102350118</a>.","short":"G.H. Choueiri, J.M. Lopez Alonso, A. Varshney, S. Sankar, B. Hof, Proceedings of the National Academy of Sciences of the United States of America 118 (2021).","ama":"Choueiri GH, Lopez Alonso JM, Varshney A, Sankar S, Hof B. Experimental observation of the origin and structure of elastoinertial turbulence. <i>Proceedings of the National Academy of Sciences of the United States of America</i>. 2021;118(45). doi:<a href=\"https://doi.org/10.1073/pnas.2102350118\">10.1073/pnas.2102350118</a>","ieee":"G. H. Choueiri, J. M. Lopez Alonso, A. Varshney, S. Sankar, and B. Hof, “Experimental observation of the origin and structure of elastoinertial turbulence,” <i>Proceedings of the National Academy of Sciences of the United States of America</i>, vol. 118, no. 45. National Academy of Sciences, 2021.","ista":"Choueiri GH, Lopez Alonso JM, Varshney A, Sankar S, Hof B. 2021. Experimental observation of the origin and structure of elastoinertial turbulence. Proceedings of the National Academy of Sciences of the United States of America. 118(45), e2102350118.","apa":"Choueiri, G. H., Lopez Alonso, J. M., Varshney, A., Sankar, S., &#38; Hof, B. (2021). Experimental observation of the origin and structure of elastoinertial turbulence. <i>Proceedings of the National Academy of Sciences of the United States of America</i>. National Academy of Sciences. <a href=\"https://doi.org/10.1073/pnas.2102350118\">https://doi.org/10.1073/pnas.2102350118</a>"},"volume":118,"intvolume":"       118","publication":"Proceedings of the National Academy of Sciences of the United States of America","acknowledgement":"We thank Y. Dubief, R. Kerswell, E. Marensi, V. Shankar, V. Steinberg, and V. Terrapon for discussions and helpful comments. A.V. and B.H. acknowledge funding from the Austrian Science Fund, grant I4188-N30, within the Deutsche Forschungsgemeinschaft research unit FOR 2688.","language":[{"iso":"eng"}],"quality_controlled":"1","doi":"10.1073/pnas.2102350118","day":"03","article_number":"e2102350118","date_published":"2021-11-03T00:00:00Z","main_file_link":[{"url":"https://arxiv.org/abs/2103.00023","open_access":"1"}],"date_updated":"2026-08-05T22:31:12Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","_id":"10299","year":"2021","month":"11","publication_identifier":{"issn":["0027-8424"],"eissn":["1091-6490"]},"abstract":[{"text":"Turbulence generally arises in shear flows if velocities and hence, inertial forces are sufficiently large. In striking contrast, viscoelastic fluids can exhibit disordered motion even at vanishing inertia. Intermediate between these cases, a state of chaotic motion, “elastoinertial turbulence” (EIT), has been observed in a narrow Reynolds number interval. We here determine the origin of EIT in experiments and show that characteristic EIT structures can be detected across an unexpectedly wide range of parameters. Close to onset, a pattern of chevron-shaped streaks emerges in qualitative agreement with linear and weakly nonlinear theory. However, in experiments, the dynamics remain weakly chaotic, and the instability can be traced to far lower Reynolds numbers than permitted by theory. For increasing inertia, the flow undergoes a transformation to a wall mode composed of inclined near-wall streaks and shear layers. This mode persists to what is known as the “maximum drag reduction limit,” and overall EIT is found to dominate viscoelastic flows across more than three orders of magnitude in Reynolds number.","lang":"eng"}],"external_id":{"pmid":[" 34732570"],"arxiv":["2103.00023"],"isi":["000720926900019"]},"pmid":1,"article_type":"original","keyword":["multidisciplinary","elastoinertial turbulence","viscoelastic flows","elastic instability","drag reduction"],"issue":"45","article_processing_charge":"No","title":"Experimental observation of the origin and structure of elastoinertial turbulence","arxiv":1,"related_material":{"record":[{"status":"public","relation":"dissertation_contains","id":"19906"}]},"publication_status":"published","date_created":"2021-11-17T13:24:24Z","oa_version":"Preprint","status":"public","oa":1,"scopus_import":"1","project":[{"call_identifier":"FWF","grant_number":"I04188","name":"Instabilities in pulsating pipe flow in complex fluids","_id":"238B8092-32DE-11EA-91FC-C7463DDC885E"}],"author":[{"id":"448BD5BC-F248-11E8-B48F-1D18A9856A87","first_name":"George H","last_name":"Choueiri","full_name":"Choueiri, George H"},{"orcid":"0000-0002-0384-2022","full_name":"Lopez Alonso, Jose M","id":"40770848-F248-11E8-B48F-1D18A9856A87","first_name":"Jose M","last_name":"Lopez Alonso"},{"id":"2A2006B2-F248-11E8-B48F-1D18A9856A87","first_name":"Atul","last_name":"Varshney","full_name":"Varshney, Atul","orcid":"0000-0002-3072-5999"},{"full_name":"Sankar, Sarath","last_name":"Sankar","first_name":"Sarath"},{"first_name":"Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","last_name":"Hof","orcid":"0000-0003-2057-2754","full_name":"Hof, Björn"}],"corr_author":"1","isi":1,"publisher":"National Academy of Sciences","department":[{"_id":"BjHo"}]},{"year":"2020","date_updated":"2026-06-18T19:23:35Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","_id":"7563","publication_identifier":{"issn":["1054-1500"],"eissn":["1089-7682"]},"month":"03","intvolume":"        30","publication":"Chaos","language":[{"iso":"eng"}],"quality_controlled":"1","citation":{"ieee":"G. Yalniz and N. B. Budanur, “Inferring symbolic dynamics of chaotic flows from persistence,” <i>Chaos</i>, vol. 30, no. 3. AIP Publishing, 2020.","mla":"Yalniz, Gökhan, and Nazmi B. Budanur. “Inferring Symbolic Dynamics of Chaotic Flows from Persistence.” <i>Chaos</i>, vol. 30, no. 3, 033109, AIP Publishing, 2020, doi:<a href=\"https://doi.org/10.1063/1.5122969\">10.1063/1.5122969</a>.","chicago":"Yalniz, Gökhan, and Nazmi B Budanur. “Inferring Symbolic Dynamics of Chaotic Flows from Persistence.” <i>Chaos</i>. AIP Publishing, 2020. <a href=\"https://doi.org/10.1063/1.5122969\">https://doi.org/10.1063/1.5122969</a>.","ama":"Yalniz G, Budanur NB. Inferring symbolic dynamics of chaotic flows from persistence. <i>Chaos</i>. 2020;30(3). doi:<a href=\"https://doi.org/10.1063/1.5122969\">10.1063/1.5122969</a>","short":"G. Yalniz, N.B. Budanur, Chaos 30 (2020).","apa":"Yalniz, G., &#38; Budanur, N. B. (2020). Inferring symbolic dynamics of chaotic flows from persistence. <i>Chaos</i>. AIP Publishing. <a href=\"https://doi.org/10.1063/1.5122969\">https://doi.org/10.1063/1.5122969</a>","ista":"Yalniz G, Budanur NB. 2020. Inferring symbolic dynamics of chaotic flows from persistence. Chaos. 30(3), 033109."},"type":"journal_article","ddc":["530"],"volume":30,"day":"03","article_number":"033109","date_published":"2020-03-03T00:00:00Z","main_file_link":[{"url":"https://doi.org/10.1063/1.5122969","open_access":"1"}],"doi":"10.1063/1.5122969","oa":1,"scopus_import":"1","status":"public","isi":1,"publisher":"AIP Publishing","department":[{"_id":"BjHo"}],"corr_author":"1","author":[{"first_name":"Gökhan","id":"66E74FA2-D8BF-11E9-8249-8DE2E5697425","last_name":"Yalniz","full_name":"Yalniz, Gökhan","orcid":"0000-0002-8490-9312"},{"full_name":"Budanur, Nazmi B","orcid":"0000-0003-0423-5010","first_name":"Nazmi B","id":"3EA1010E-F248-11E8-B48F-1D18A9856A87","last_name":"Budanur"}],"article_type":"original","external_id":{"isi":["000519254800002"],"arxiv":["1910.04584"]},"abstract":[{"text":"We introduce “state space persistence analysis” for deducing the symbolic dynamics of time series data obtained from high-dimensional chaotic attractors. To this end, we adapt a topological data analysis technique known as persistent homology for the characterization of state space projections of chaotic trajectories and periodic orbits. By comparing the shapes along a chaotic trajectory to those of the periodic orbits, state space persistence analysis quantifies the shape similarity of chaotic trajectory segments and periodic orbits. We demonstrate the method by applying it to the three-dimensional Rössler system and a 30-dimensional discretization of the Kuramoto–Sivashinsky partial differential equation in (1+1) dimensions.\r\nOne way of studying chaotic attractors systematically is through their symbolic dynamics, in which one partitions the state space into qualitatively different regions and assigns a symbol to each such region.1–3 This yields a “coarse-grained” state space of the system, which can then be reduced to a Markov chain encoding all possible transitions between the states of the system. While it is possible to obtain the symbolic dynamics of low-dimensional chaotic systems with standard tools such as Poincaré maps, when applied to high-dimensional systems such as turbulent flows, these tools alone are not sufficient to determine symbolic dynamics.4,5 In this paper, we develop “state space persistence analysis” and demonstrate that it can be utilized to infer the symbolic dynamics in very high-dimensional settings.","lang":"eng"}],"title":"Inferring symbolic dynamics of chaotic flows from persistence","article_processing_charge":"No","arxiv":1,"oa_version":"Published Version","publication_status":"published","date_created":"2020-03-04T08:06:25Z","related_material":{"record":[{"status":"public","relation":"dissertation_contains","id":"19684"}]},"issue":"3"},{"department":[{"_id":"BjHo"}],"publisher":"National Academy of Sciences","isi":1,"project":[{"grant_number":"I04188","name":"Instabilities in pulsating pipe flow in complex fluids","call_identifier":"FWF","_id":"238B8092-32DE-11EA-91FC-C7463DDC885E"},{"call_identifier":"H2020","grant_number":"754411","name":"ISTplus - Postdoctoral Fellowships","_id":"260C2330-B435-11E9-9278-68D0E5697425"}],"author":[{"first_name":"Duo","id":"3454D55E-F248-11E8-B48F-1D18A9856A87","last_name":"Xu","full_name":"Xu, Duo"},{"first_name":"Atul","id":"2A2006B2-F248-11E8-B48F-1D18A9856A87","last_name":"Varshney","orcid":"0000-0002-3072-5999","full_name":"Varshney, Atul"},{"orcid":"0000-0002-0179-9737","full_name":"Ma, Xingyu","last_name":"Ma","first_name":"Xingyu","id":"34BADBA6-F248-11E8-B48F-1D18A9856A87"},{"first_name":"Baofang","last_name":"Song","full_name":"Song, Baofang"},{"last_name":"Riedl","first_name":"Michael","id":"3BE60946-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0003-4844-6311","full_name":"Riedl, Michael"},{"full_name":"Avila, Marc","last_name":"Avila","first_name":"Marc"},{"id":"3A374330-F248-11E8-B48F-1D18A9856A87","first_name":"Björn","last_name":"Hof","orcid":"0000-0003-2057-2754","full_name":"Hof, Björn"}],"oa":1,"scopus_import":"1","status":"public","oa_version":"Preprint","publication_status":"published","related_material":{"link":[{"description":"News on IST Homepage","relation":"press_release","url":"https://ist.ac.at/en/news/blood-flows-more-turbulent-than-previously-expected/"}],"record":[{"relation":"dissertation_contains","status":"public","id":"12726"},{"relation":"dissertation_contains","status":"public","id":"14530"}]},"date_created":"2020-06-07T22:00:51Z","title":"Nonlinear hydrodynamic instability and turbulence in pulsatile flow","article_processing_charge":"No","arxiv":1,"issue":"21","article_type":"original","pmid":1,"abstract":[{"lang":"eng","text":"Pulsating flows through tubular geometries are laminar provided that velocities are moderate. This in particular is also believed to apply to cardiovascular flows where inertial forces are typically too low to sustain turbulence. On the other hand, flow instabilities and fluctuating shear stresses are held responsible for a variety of cardiovascular diseases. Here we report a nonlinear instability mechanism for pulsating pipe flow that gives rise to bursts of turbulence at low flow rates. Geometrical distortions of small, yet finite, amplitude are found to excite a state consisting of helical vortices during flow deceleration. The resulting flow pattern grows rapidly in magnitude, breaks down into turbulence, and eventually returns to laminar when the flow accelerates. This scenario causes shear stress fluctuations and flow reversal during each pulsation cycle. Such unsteady conditions can adversely affect blood vessels and have been shown to promote inflammation and dysfunction of the shear stress-sensitive endothelial cell layer."}],"external_id":{"isi":["000536797100014"],"arxiv":["2005.11190"],"pmid":["32393637"]},"page":"11233-11239","ec_funded":1,"publication_identifier":{"eissn":["1091-6490"],"issn":["0027-8424"]},"month":"05","year":"2020","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","_id":"7932","date_updated":"2026-04-07T13:29:13Z","date_published":"2020-05-26T00:00:00Z","main_file_link":[{"url":"https://arxiv.org/abs/2005.11190","open_access":"1"}],"day":"26","doi":"10.1073/pnas.1913716117","language":[{"iso":"eng"}],"quality_controlled":"1","intvolume":"       117","publication":"Proceedings of the National Academy of Sciences of the United States of America","volume":117,"type":"journal_article","citation":{"ieee":"D. Xu <i>et al.</i>, “Nonlinear hydrodynamic instability and turbulence in pulsatile flow,” <i>Proceedings of the National Academy of Sciences of the United States of America</i>, vol. 117, no. 21. National Academy of Sciences, pp. 11233–11239, 2020.","chicago":"Xu, Duo, Atul Varshney, Xingyu Ma, Baofang Song, Michael Riedl, Marc Avila, and Björn Hof. “Nonlinear Hydrodynamic Instability and Turbulence in Pulsatile Flow.” <i>Proceedings of the National Academy of Sciences of the United States of America</i>. National Academy of Sciences, 2020. <a href=\"https://doi.org/10.1073/pnas.1913716117\">https://doi.org/10.1073/pnas.1913716117</a>.","mla":"Xu, Duo, et al. “Nonlinear Hydrodynamic Instability and Turbulence in Pulsatile Flow.” <i>Proceedings of the National Academy of Sciences of the United States of America</i>, vol. 117, no. 21, National Academy of Sciences, 2020, pp. 11233–39, doi:<a href=\"https://doi.org/10.1073/pnas.1913716117\">10.1073/pnas.1913716117</a>.","ama":"Xu D, Varshney A, Ma X, et al. Nonlinear hydrodynamic instability and turbulence in pulsatile flow. <i>Proceedings of the National Academy of Sciences of the United States of America</i>. 2020;117(21):11233-11239. doi:<a href=\"https://doi.org/10.1073/pnas.1913716117\">10.1073/pnas.1913716117</a>","short":"D. Xu, A. Varshney, X. Ma, B. Song, M. Riedl, M. Avila, B. Hof, Proceedings of the National Academy of Sciences of the United States of America 117 (2020) 11233–11239.","apa":"Xu, D., Varshney, A., Ma, X., Song, B., Riedl, M., Avila, M., &#38; Hof, B. (2020). Nonlinear hydrodynamic instability and turbulence in pulsatile flow. <i>Proceedings of the National Academy of Sciences of the United States of America</i>. National Academy of Sciences. <a href=\"https://doi.org/10.1073/pnas.1913716117\">https://doi.org/10.1073/pnas.1913716117</a>","ista":"Xu D, Varshney A, Ma X, Song B, Riedl M, Avila M, Hof B. 2020. Nonlinear hydrodynamic instability and turbulence in pulsatile flow. Proceedings of the National Academy of Sciences of the United States of America. 117(21), 11233–11239."}},{"has_accepted_license":"1","status":"public","tmp":{"short":"CC BY-NC-SA (4.0)","name":"Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)","legal_code_url":"https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode","image":"/images/cc_by_nc_sa.png"},"scopus_import":"1","oa":1,"corr_author":"1","author":[{"full_name":"Paranjape, Chaitanya S","first_name":"Chaitanya S","id":"3D85B7C4-F248-11E8-B48F-1D18A9856A87","last_name":"Paranjape"},{"full_name":"Duguet, Yohann","first_name":"Yohann","last_name":"Duguet"},{"first_name":"Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","last_name":"Hof","orcid":"0000-0003-2057-2754","full_name":"Hof, Björn"}],"isi":1,"publisher":"Cambridge University Press","department":[{"_id":"BjHo"}],"external_id":{"isi":["000539132300001"]},"abstract":[{"lang":"eng","text":"With decreasing Reynolds number, Re, turbulence in channel flow becomes spatio-temporally intermittent and self-organises into solitary stripes oblique to the mean flow direction. We report here the existence of localised nonlinear travelling wave solutions of the Navier–Stokes equations possessing this obliqueness property. Such solutions are identified numerically using edge tracking coupled with arclength continuation. All solutions emerge in saddle-node bifurcations at values of Re lower than the non-localised solutions. Relative periodic orbit solutions bifurcating from branches of travelling waves have also been computed. A complete parametric study is performed, including their stability, the investigation of their large-scale flow, and the robustness to changes of the numerical domain."}],"file":[{"file_size":767873,"file_id":"8070","date_updated":"2020-07-14T12:48:08Z","checksum":"3f487bf6d9286787096306eaa18702e8","access_level":"open_access","date_created":"2020-06-30T08:37:37Z","relation":"main_file","content_type":"application/pdf","file_name":"2020_JournalOfFluidMech_Paranjape.pdf","creator":"cziletti"}],"license":"https://creativecommons.org/licenses/by-nc-sa/4.0/","file_date_updated":"2020-07-14T12:48:08Z","article_type":"original","article_processing_charge":"Yes (via OA deal)","title":"Oblique stripe solutions of channel flow","publication_status":"published","date_created":"2020-06-29T07:59:35Z","oa_version":"Published Version","date_updated":"2025-07-10T11:55:03Z","_id":"8043","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","year":"2020","month":"08","publication_identifier":{"issn":["0022-1120"],"eissn":["1469-7645"]},"type":"journal_article","citation":{"ieee":"C. S. Paranjape, Y. Duguet, and B. Hof, “Oblique stripe solutions of channel flow,” <i>Journal of Fluid Mechanics</i>, vol. 897. Cambridge University Press, 2020.","ama":"Paranjape CS, Duguet Y, Hof B. Oblique stripe solutions of channel flow. <i>Journal of Fluid Mechanics</i>. 2020;897. doi:<a href=\"https://doi.org/10.1017/jfm.2020.322\">10.1017/jfm.2020.322</a>","short":"C.S. Paranjape, Y. Duguet, B. Hof, Journal of Fluid Mechanics 897 (2020).","chicago":"Paranjape, Chaitanya S, Yohann Duguet, and Björn Hof. “Oblique Stripe Solutions of Channel Flow.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2020. <a href=\"https://doi.org/10.1017/jfm.2020.322\">https://doi.org/10.1017/jfm.2020.322</a>.","mla":"Paranjape, Chaitanya S., et al. “Oblique Stripe Solutions of Channel Flow.” <i>Journal of Fluid Mechanics</i>, vol. 897, A7, Cambridge University Press, 2020, doi:<a href=\"https://doi.org/10.1017/jfm.2020.322\">10.1017/jfm.2020.322</a>.","apa":"Paranjape, C. S., Duguet, Y., &#38; Hof, B. (2020). Oblique stripe solutions of channel flow. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2020.322\">https://doi.org/10.1017/jfm.2020.322</a>","ista":"Paranjape CS, Duguet Y, Hof B. 2020. Oblique stripe solutions of channel flow. Journal of Fluid Mechanics. 897, A7."},"volume":897,"ddc":["530"],"publication":"Journal of Fluid Mechanics","acknowledgement":"The authors thank S. Zammert and B. Budanur for useful discussions. J. F. Gibson is gratefully acknowledged for the development and the maintenance of the code Channelflow. Y.D. would like to thank P. Schlatter and D. S. Henningson for an early collaboration on a similar topic in the case of plane Couette flow during the years 2008–2013.","intvolume":"       897","quality_controlled":"1","language":[{"iso":"eng"}],"doi":"10.1017/jfm.2020.322","day":"25","article_number":"A7","date_published":"2020-08-25T00:00:00Z"},{"volume":125,"type":"journal_article","citation":{"mla":"Suri, Balachandra, et al. “Capturing Turbulent Dynamics and Statistics in Experiments with Unstable Periodic Orbits.” <i>Physical Review Letters</i>, vol. 125, no. 6, 064501, American Physical Society, 2020, doi:<a href=\"https://doi.org/10.1103/physrevlett.125.064501\">10.1103/physrevlett.125.064501</a>.","chicago":"Suri, Balachandra, Logan Kageorge, Roman O. Grigoriev, and Michael F. Schatz. “Capturing Turbulent Dynamics and Statistics in Experiments with Unstable Periodic Orbits.” <i>Physical Review Letters</i>. American Physical Society, 2020. <a href=\"https://doi.org/10.1103/physrevlett.125.064501\">https://doi.org/10.1103/physrevlett.125.064501</a>.","short":"B. Suri, L. Kageorge, R.O. Grigoriev, M.F. Schatz, Physical Review Letters 125 (2020).","ama":"Suri B, Kageorge L, Grigoriev RO, Schatz MF. Capturing turbulent dynamics and statistics in experiments with unstable periodic orbits. <i>Physical Review Letters</i>. 2020;125(6). doi:<a href=\"https://doi.org/10.1103/physrevlett.125.064501\">10.1103/physrevlett.125.064501</a>","ieee":"B. Suri, L. Kageorge, R. O. Grigoriev, and M. F. Schatz, “Capturing turbulent dynamics and statistics in experiments with unstable periodic orbits,” <i>Physical Review Letters</i>, vol. 125, no. 6. American Physical Society, 2020.","ista":"Suri B, Kageorge L, Grigoriev RO, Schatz MF. 2020. Capturing turbulent dynamics and statistics in experiments with unstable periodic orbits. Physical Review Letters. 125(6), 064501.","apa":"Suri, B., Kageorge, L., Grigoriev, R. O., &#38; Schatz, M. F. (2020). Capturing turbulent dynamics and statistics in experiments with unstable periodic orbits. <i>Physical Review Letters</i>. American Physical Society. <a href=\"https://doi.org/10.1103/physrevlett.125.064501\">https://doi.org/10.1103/physrevlett.125.064501</a>"},"quality_controlled":"1","language":[{"iso":"eng"}],"acknowledgement":"M. F. S. and R. O. G. acknowledge funding from the National Science Foundation (CMMI-1234436, DMS1125302, CMMI-1725587) and Defense Advanced Research Projects Agency (HR0011-16-2-0033). B. S.has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007–2013/ under REA Grant Agreement No. 291734.","publication":"Physical Review Letters","intvolume":"       125","doi":"10.1103/physrevlett.125.064501","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/2008.02367"}],"date_published":"2020-08-05T00:00:00Z","article_number":"064501","day":"05","_id":"8634","user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","date_updated":"2025-04-15T06:50:02Z","year":"2020","month":"08","ec_funded":1,"publication_identifier":{"issn":["0031-9007"],"eissn":["1079-7114"]},"abstract":[{"text":"In laboratory studies and numerical simulations, we observe clear signatures of unstable time-periodic solutions in a moderately turbulent quasi-two-dimensional flow. We validate the dynamical relevance of such solutions by demonstrating that turbulent flows in both experiment and numerics transiently display time-periodic dynamics when they shadow unstable periodic orbits (UPOs). We show that UPOs we computed are also statistically significant, with turbulent flows spending a sizable fraction of the total time near these solutions. As a result, the average rates of energy input and dissipation for the turbulent flow and frequently visited UPOs differ only by a few percent.","lang":"eng"}],"external_id":{"isi":["000555785600005"],"arxiv":["2008.02367"]},"keyword":["General Physics and Astronomy"],"article_type":"original","issue":"6","date_created":"2020-10-08T17:27:32Z","publication_status":"published","oa_version":"Preprint","arxiv":1,"article_processing_charge":"No","title":"Capturing turbulent dynamics and statistics in experiments with unstable periodic orbits","status":"public","scopus_import":"1","oa":1,"author":[{"full_name":"Suri, Balachandra","id":"47A5E706-F248-11E8-B48F-1D18A9856A87","first_name":"Balachandra","last_name":"Suri"},{"first_name":"Logan","last_name":"Kageorge","full_name":"Kageorge, Logan"},{"first_name":"Roman O.","last_name":"Grigoriev","full_name":"Grigoriev, Roman O."},{"first_name":"Michael F.","last_name":"Schatz","full_name":"Schatz, Michael F."}],"project":[{"grant_number":"291734","name":"International IST Postdoc Fellowship Programme","call_identifier":"FP7","_id":"25681D80-B435-11E9-9278-68D0E5697425"}],"publisher":"American Physical Society","department":[{"_id":"BjHo"}],"isi":1},{"date_updated":"2026-04-02T14:16:50Z","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","_id":"7364","year":"2020","month":"01","publication_identifier":{"eissn":["2352-7110"]},"type":"journal_article","citation":{"ieee":"J. M. Lopez Alonso, D. Feldmann, M. Rampp, A. Vela-Martín, L. Shi, and M. Avila, “nsCouette – A high-performance code for direct numerical simulations of turbulent Taylor–Couette flow,” <i>SoftwareX</i>, vol. 11. Elsevier, 2020.","chicago":"Lopez Alonso, Jose M, Daniel Feldmann, Markus Rampp, Alberto Vela-Martín, Liang Shi, and Marc Avila. “NsCouette – A High-Performance Code for Direct Numerical Simulations of Turbulent Taylor–Couette Flow.” <i>SoftwareX</i>. Elsevier, 2020. <a href=\"https://doi.org/10.1016/j.softx.2019.100395\">https://doi.org/10.1016/j.softx.2019.100395</a>.","mla":"Lopez Alonso, Jose M., et al. “NsCouette – A High-Performance Code for Direct Numerical Simulations of Turbulent Taylor–Couette Flow.” <i>SoftwareX</i>, vol. 11, 100395, Elsevier, 2020, doi:<a href=\"https://doi.org/10.1016/j.softx.2019.100395\">10.1016/j.softx.2019.100395</a>.","short":"J.M. Lopez Alonso, D. Feldmann, M. Rampp, A. Vela-Martín, L. Shi, M. Avila, SoftwareX 11 (2020).","ama":"Lopez Alonso JM, Feldmann D, Rampp M, Vela-Martín A, Shi L, Avila M. nsCouette – A high-performance code for direct numerical simulations of turbulent Taylor–Couette flow. <i>SoftwareX</i>. 2020;11. doi:<a href=\"https://doi.org/10.1016/j.softx.2019.100395\">10.1016/j.softx.2019.100395</a>","apa":"Lopez Alonso, J. M., Feldmann, D., Rampp, M., Vela-Martín, A., Shi, L., &#38; Avila, M. (2020). nsCouette – A high-performance code for direct numerical simulations of turbulent Taylor–Couette flow. <i>SoftwareX</i>. Elsevier. <a href=\"https://doi.org/10.1016/j.softx.2019.100395\">https://doi.org/10.1016/j.softx.2019.100395</a>","ista":"Lopez Alonso JM, Feldmann D, Rampp M, Vela-Martín A, Shi L, Avila M. 2020. nsCouette – A high-performance code for direct numerical simulations of turbulent Taylor–Couette flow. SoftwareX. 11, 100395."},"ddc":["000"],"volume":11,"intvolume":"        11","publication":"SoftwareX","language":[{"iso":"eng"}],"quality_controlled":"1","doi":"10.1016/j.softx.2019.100395","day":"17","article_number":"100395","date_published":"2020-01-17T00:00:00Z","has_accepted_license":"1","status":"public","tmp":{"short":"CC BY-NC-ND (4.0)","image":"/images/cc_by_nc_nd.png","legal_code_url":"https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode","name":"Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)"},"oa":1,"scopus_import":"1","author":[{"orcid":"0000-0002-0384-2022","full_name":"Lopez Alonso, Jose M","first_name":"Jose M","id":"40770848-F248-11E8-B48F-1D18A9856A87","last_name":"Lopez Alonso"},{"last_name":"Feldmann","first_name":"Daniel","full_name":"Feldmann, Daniel"},{"first_name":"Markus","last_name":"Rampp","full_name":"Rampp, Markus"},{"full_name":"Vela-Martín, Alberto","last_name":"Vela-Martín","first_name":"Alberto"},{"id":"374A3F1A-F248-11E8-B48F-1D18A9856A87","first_name":"Liang","last_name":"Shi","full_name":"Shi, Liang"},{"full_name":"Avila, Marc","first_name":"Marc","last_name":"Avila"}],"corr_author":"1","isi":1,"publisher":"Elsevier","department":[{"_id":"BjHo"}],"abstract":[{"lang":"eng","text":"We present nsCouette, a highly scalable software tool to solve the Navier–Stokes equations for incompressible fluid flow between differentially heated and independently rotating, concentric cylinders. It is based on a pseudospectral spatial discretization and dynamic time-stepping. It is implemented in modern Fortran with a hybrid MPI-OpenMP parallelization scheme and thus designed to compute turbulent flows at high Reynolds and Rayleigh numbers. An additional GPU implementation (C-CUDA) for intermediate problem sizes and a version for pipe flow (nsPipe) are also provided."}],"external_id":{"isi":["000552271200011"],"arxiv":["1908.00587"]},"file":[{"file_size":679707,"file_id":"7365","date_updated":"2020-07-14T12:47:56Z","checksum":"2af1a1a3cc33557b345145276f221668","date_created":"2020-01-27T07:32:46Z","access_level":"open_access","creator":"dernst","content_type":"application/pdf","relation":"main_file","file_name":"2020_SoftwareX_Lopez.pdf"}],"article_type":"original","file_date_updated":"2020-07-14T12:47:56Z","title":"nsCouette – A high-performance code for direct numerical simulations of turbulent Taylor–Couette flow","article_processing_charge":"No","arxiv":1,"date_created":"2020-01-26T23:00:35Z","oa_version":"Published Version","publication_status":"published"},{"article_type":"original","external_id":{"arxiv":["1912.09270"],"isi":["000515065100001"]},"abstract":[{"lang":"eng","text":"In the past two decades, our understanding of the transition to turbulence in shear flows with linearly stable laminar solutions has greatly improved. Regarding the susceptibility of the laminar flow, two concepts have been particularly useful: the edge states and the minimal seeds. In this nonlinear picture of the transition, the basin boundary of turbulence is set by the edge state's stable manifold and this manifold comes closest in energy to the laminar equilibrium at the minimal seed. We begin this paper by presenting numerical experiments in which three-dimensional perturbations are too energetic to trigger turbulence in pipe flow but they do lead to turbulence when their amplitude is reduced. We show that this seemingly counterintuitive observation is in fact consistent with the fully nonlinear description of the transition mediated by the edge state. In order to understand the physical mechanisms behind this process, we measure the turbulent kinetic energy production and dissipation rates as a function of the radial coordinate. Our main observation is that the transition to turbulence relies on the energy amplification away from the wall, as opposed to the turbulence itself, whose energy is predominantly produced near the wall. This observation is further supported by the similar analyses on the minimal seeds and the edge states. Furthermore, we show that the time evolution of production-over-dissipation curves provides a clear distinction between the different initial amplification stages of the transition to turbulence from the minimal seed."}],"date_created":"2020-02-27T10:26:57Z","oa_version":"Preprint","publication_status":"published","article_processing_charge":"No","title":"Upper edge of chaos and the energetics of transition in pipe flow","arxiv":1,"issue":"2","oa":1,"scopus_import":"1","status":"public","publisher":"American Physical Society","department":[{"_id":"BjHo"}],"isi":1,"author":[{"orcid":"0000-0003-0423-5010","full_name":"Budanur, Nazmi B","first_name":"Nazmi B","id":"3EA1010E-F248-11E8-B48F-1D18A9856A87","last_name":"Budanur"},{"full_name":"Marensi, Elena","last_name":"Marensi","first_name":"Elena"},{"last_name":"Willis","first_name":"Ashley P.","full_name":"Willis, Ashley P."},{"first_name":"Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","last_name":"Hof","full_name":"Hof, Björn","orcid":"0000-0003-2057-2754"}],"language":[{"iso":"eng"}],"quality_controlled":"1","intvolume":"         5","publication":"Physical Review Fluids","volume":5,"type":"journal_article","citation":{"ista":"Budanur NB, Marensi E, Willis AP, Hof B. 2020. Upper edge of chaos and the energetics of transition in pipe flow. Physical Review Fluids. 5(2), 023903.","apa":"Budanur, N. B., Marensi, E., Willis, A. P., &#38; Hof, B. (2020). Upper edge of chaos and the energetics of transition in pipe flow. <i>Physical Review Fluids</i>. American Physical Society. <a href=\"https://doi.org/10.1103/physrevfluids.5.023903\">https://doi.org/10.1103/physrevfluids.5.023903</a>","short":"N.B. Budanur, E. Marensi, A.P. Willis, B. Hof, Physical Review Fluids 5 (2020).","ama":"Budanur NB, Marensi E, Willis AP, Hof B. Upper edge of chaos and the energetics of transition in pipe flow. <i>Physical Review Fluids</i>. 2020;5(2). doi:<a href=\"https://doi.org/10.1103/physrevfluids.5.023903\">10.1103/physrevfluids.5.023903</a>","chicago":"Budanur, Nazmi B, Elena Marensi, Ashley P. Willis, and Björn Hof. “Upper Edge of Chaos and the Energetics of Transition in Pipe Flow.” <i>Physical Review Fluids</i>. American Physical Society, 2020. <a href=\"https://doi.org/10.1103/physrevfluids.5.023903\">https://doi.org/10.1103/physrevfluids.5.023903</a>.","mla":"Budanur, Nazmi B., et al. “Upper Edge of Chaos and the Energetics of Transition in Pipe Flow.” <i>Physical Review Fluids</i>, vol. 5, no. 2, 023903, American Physical Society, 2020, doi:<a href=\"https://doi.org/10.1103/physrevfluids.5.023903\">10.1103/physrevfluids.5.023903</a>.","ieee":"N. B. Budanur, E. Marensi, A. P. Willis, and B. Hof, “Upper edge of chaos and the energetics of transition in pipe flow,” <i>Physical Review Fluids</i>, vol. 5, no. 2. American Physical Society, 2020."},"article_number":"023903","date_published":"2020-02-21T00:00:00Z","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1912.09270"}],"day":"21","doi":"10.1103/physrevfluids.5.023903","year":"2020","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","_id":"7534","date_updated":"2023-08-18T06:44:46Z","publication_identifier":{"issn":["2469-990X"]},"month":"02"},{"doi":"10.15479/AT:ISTA:8350","date_published":"2020-09-09T00:00:00Z","day":"09","ddc":["570"],"type":"dissertation","citation":{"short":"S. Shamipour, Bulk Actin Dynamics Drive Phase Segregation in Zebrafish Oocytes , Institute of Science and Technology Austria, 2020.","ama":"Shamipour S. Bulk actin dynamics drive phase segregation in zebrafish oocytes . 2020. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:8350\">10.15479/AT:ISTA:8350</a>","mla":"Shamipour, Shayan. <i>Bulk Actin Dynamics Drive Phase Segregation in Zebrafish Oocytes </i>. Institute of Science and Technology Austria, 2020, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:8350\">10.15479/AT:ISTA:8350</a>.","chicago":"Shamipour, Shayan. “Bulk Actin Dynamics Drive Phase Segregation in Zebrafish Oocytes .” Institute of Science and Technology Austria, 2020. <a href=\"https://doi.org/10.15479/AT:ISTA:8350\">https://doi.org/10.15479/AT:ISTA:8350</a>.","ieee":"S. Shamipour, “Bulk actin dynamics drive phase segregation in zebrafish oocytes ,” Institute of Science and Technology Austria, 2020.","ista":"Shamipour S. 2020. Bulk actin dynamics drive phase segregation in zebrafish oocytes . Institute of Science and Technology Austria.","apa":"Shamipour, S. (2020). <i>Bulk actin dynamics drive phase segregation in zebrafish oocytes </i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:8350\">https://doi.org/10.15479/AT:ISTA:8350</a>"},"language":[{"iso":"eng"}],"acknowledgement":"I would have had no fish and hence no results without our wonderful fish facility crew, Verena Mayer, Eva Schlegl, Andreas Mlak and Matthias Nowak. Special thanks to Verena for being always happy to help and dealing with our chaotic schedules in the lab. Danke auch, Verena, für deine Geduld, mit mir auf Deutsch zu sprechen. Das hat mir sehr geholfen.\r\nSpecial thanks to the Bioimaging and EM facilities at IST Austria for supporting us every day. Very special thanks would go to Robert Hauschild for his continuous support on data analysis and also to Jack Merrin for designing and building microfabricated chambers for the project and for the various discussions on making zebrafish extracts.","month":"09","acknowledged_ssus":[{"_id":"PreCl"},{"_id":"Bio"},{"_id":"EM-Fac"}],"publication_identifier":{"issn":["2663-337X"]},"supervisor":[{"id":"39427864-F248-11E8-B48F-1D18A9856A87","first_name":"Carl-Philipp J","last_name":"Heisenberg","full_name":"Heisenberg, Carl-Philipp J","orcid":"0000-0002-0912-4566"},{"full_name":"Hof, Björn","orcid":"0000-0003-2057-2754","id":"3A374330-F248-11E8-B48F-1D18A9856A87","first_name":"Björn","last_name":"Hof"}],"_id":"8350","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","date_updated":"2025-09-11T07:08:52Z","year":"2020","related_material":{"record":[{"status":"public","relation":"part_of_dissertation","id":"7001"},{"relation":"part_of_dissertation","status":"public","id":"6508"},{"id":"735","status":"public","relation":"part_of_dissertation"},{"id":"661","status":"public","relation":"part_of_dissertation"}]},"publication_status":"published","date_created":"2020-09-09T11:12:10Z","oa_version":"None","title":"Bulk actin dynamics drive phase segregation in zebrafish oocytes ","article_processing_charge":"No","file":[{"file_size":65194814,"file_id":"8351","date_updated":"2021-09-11T22:30:05Z","checksum":"6e47871c74f85008b9876112eb3fcfa1","date_created":"2020-09-09T11:06:27Z","embargo_to":"open_access","access_level":"closed","creator":"sshamip","relation":"source_file","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","file_name":"Shayan-Thesis-Final.docx"},{"file_id":"8352","file_size":23729605,"date_updated":"2021-09-11T22:30:05Z","access_level":"open_access","date_created":"2020-09-09T11:06:13Z","checksum":"1b44c57f04d7e8a6fe41b1c9c55a52a3","embargo":"2021-09-10","relation":"main_file","content_type":"application/pdf","file_name":"Shayan-Thesis-Final.pdf","creator":"sshamip"}],"page":"107","abstract":[{"text":"Cytoplasm is a gel-like crowded environment composed of tens of thousands of macromolecules, organelles, cytoskeletal networks and cytosol. The structure of the cytoplasm is thought to be highly organized and heterogeneous due to the crowding of its constituents and their effective compartmentalization. In such an environment, the diffusive dynamics of the molecules is very restricted, an effect that is further amplified by clustering and anchoring of molecules. Despite the jammed nature of the cytoplasm at the microscopic scale, large-scale reorganization of cytoplasm is essential for important cellular functions, such as nuclear positioning and cell division. How such mesoscale reorganization of the cytoplasm is achieved, especially for very large cells such as oocytes or syncytial tissues that can span hundreds of micrometers in size, has only begun to be understood.\r\nIn this thesis, I focus on the recent advances in elucidating the molecular, cellular and biophysical principles underlying cytoplasmic organization across different scales, structures and species. First, I outline which of these principles have been identified by reductionist approaches, such as in vitro reconstitution assays, where boundary conditions and components can be modulated at ease. I then describe how the theoretical and experimental framework established in these reduced systems have been applied to their more complex in vivo counterparts, in particular oocytes and embryonic syncytial structures, and discuss how such complex biological systems can initiate symmetry breaking and establish patterning.\r\nSpecifically, I examine an example of large-scale reorganizations taking place in zebrafish embryos, where extensive cytoplasmic streaming leads to the segregation of cytoplasm from yolk granules along the animal-vegetal axis of the embryo. Using biophysical experimentation and theory, I investigate the forces underlying this process, to show that this process does not rely on cortical actin reorganization, as previously thought, but instead on a cell-cycle-dependent bulk actin polymerization wave traveling from the animal to the vegetal pole of the embryo. This wave functions in segregation by both pulling cytoplasm animally and pushing yolk granules vegetally. Cytoplasm pulling is mediated by bulk actin network flows exerting friction forces on the cytoplasm, while yolk granule pushing is achieved by a mechanism closely resembling actin comet formation on yolk granules. This study defines a novel role of bulk actin polymerization waves in embryo polarization via cytoplasmic segregation. Lastly, I describe the cytoplasmic reorganizations taking place during zebrafish oocyte maturation, where the initial segregation of the cytoplasm and yolk granules occurs. Here, I demonstrate a previously uncharacterized wave of microtubule aster formation, traveling the oocyte along the animal-vegetal axis. Further research is required to determine the role of such microtubule structures in cytoplasmic reorganizations therein.\r\nCollectively, these studies provide further evidence for the coupling between cell cytoskeleton and cell cycle machinery, which can underlie a core self-organizing mechanism for orchestrating large-scale reorganizations in a cell-cycle-tunable manner, where the modulations of the force-generating machinery and cytoplasmic mechanics can be harbored to fulfill cellular functions.","lang":"eng"}],"degree_awarded":"PhD","file_date_updated":"2021-09-11T22:30:05Z","corr_author":"1","author":[{"full_name":"Shamipour, Shayan","first_name":"Shayan","id":"40B34FE2-F248-11E8-B48F-1D18A9856A87","last_name":"Shamipour"}],"alternative_title":["ISTA Thesis"],"publisher":"Institute of Science and Technology Austria","department":[{"_id":"BjHo"},{"_id":"CaHe"}],"has_accepted_license":"1","status":"public","oa":1},{"doi":"10.15479/AT:ISTA:7258","date_published":"2020-01-13T00:00:00Z","day":"13","ddc":["532"],"type":"dissertation","citation":{"ieee":"D. Scarselli, “New approaches to reduce friction in turbulent pipe flow,” Institute of Science and Technology Austria, 2020.","short":"D. Scarselli, New Approaches to Reduce Friction in Turbulent Pipe Flow, Institute of Science and Technology Austria, 2020.","ama":"Scarselli D. New approaches to reduce friction in turbulent pipe flow. 2020. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:7258\">10.15479/AT:ISTA:7258</a>","chicago":"Scarselli, Davide. “New Approaches to Reduce Friction in Turbulent Pipe Flow.” Institute of Science and Technology Austria, 2020. <a href=\"https://doi.org/10.15479/AT:ISTA:7258\">https://doi.org/10.15479/AT:ISTA:7258</a>.","mla":"Scarselli, Davide. <i>New Approaches to Reduce Friction in Turbulent Pipe Flow</i>. Institute of Science and Technology Austria, 2020, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:7258\">10.15479/AT:ISTA:7258</a>.","apa":"Scarselli, D. (2020). <i>New approaches to reduce friction in turbulent pipe flow</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:7258\">https://doi.org/10.15479/AT:ISTA:7258</a>","ista":"Scarselli D. 2020. New approaches to reduce friction in turbulent pipe flow. Institute of Science and Technology Austria."},"language":[{"iso":"eng"}],"month":"01","ec_funded":1,"publication_identifier":{"issn":["2663-337X"]},"user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","_id":"7258","supervisor":[{"orcid":"0000-0003-2057-2754","full_name":"Hof, Björn","last_name":"Hof","id":"3A374330-F248-11E8-B48F-1D18A9856A87","first_name":"Björn"}],"date_updated":"2026-04-08T07:28:22Z","year":"2020","OA_place":"publisher","related_material":{"record":[{"id":"422","relation":"part_of_dissertation","status":"public"},{"status":"public","relation":"part_of_dissertation","id":"461"},{"id":"6228","status":"public","relation":"part_of_dissertation"},{"id":"6486","relation":"part_of_dissertation","status":"public"}]},"oa_version":"None","publication_status":"published","date_created":"2020-01-12T16:07:26Z","title":"New approaches to reduce friction in turbulent pipe flow","article_processing_charge":"No","file":[{"date_created":"2020-01-12T15:57:14Z","embargo_to":"open_access","access_level":"closed","checksum":"4df1ab24e9896635106adde5a54615bf","creator":"dscarsel","content_type":"application/zip","relation":"source_file","file_name":"2020_Scarselli_Thesis.zip","file_id":"7259","file_size":26640830,"date_updated":"2021-01-13T23:30:05Z"},{"file_size":8515844,"file_id":"7260","date_updated":"2021-01-13T23:30:05Z","checksum":"48659ab98e3414293c7a721385c2fd1c","access_level":"open_access","date_created":"2020-01-12T15:56:14Z","file_name":"2020_Scarselli_Thesis.pdf","relation":"main_file","content_type":"application/pdf","creator":"dscarsel","embargo":"2021-01-12"}],"abstract":[{"lang":"eng","text":"Many flows encountered in nature and applications are characterized by a chaotic motion known as turbulence. Turbulent flows generate intense friction with pipe walls and are responsible for considerable amounts of energy losses at world scale. The nature of turbulent friction and techniques aimed at reducing it have been subject of extensive research over the last century, but no definite answer has been found yet. In this thesis we show that in pipes at moderate turbulent Reynolds numbers friction is better described by the power law first introduced by Blasius and not by the Prandtl–von Kármán formula. At higher Reynolds numbers, large scale motions gradually become more important in the flow and can be related to the change in scaling of friction. Next, we present a series of new techniques that can relaminarize turbulence by suppressing a key mechanism that regenerates it at walls, the lift–up effect. In addition, we investigate the process of turbulence decay in several experiments and discuss the drag reduction potential. Finally, we examine the behavior of friction under pulsating conditions inspired by the human heart cycle and we show that under such circumstances turbulent friction can be reduced to produce energy savings."}],"page":"174","degree_awarded":"PhD","file_date_updated":"2021-01-13T23:30:05Z","project":[{"grant_number":"306589","name":"Decoding the complexity of turbulence at its origin","call_identifier":"FP7","_id":"25152F3A-B435-11E9-9278-68D0E5697425"},{"_id":"25104D44-B435-11E9-9278-68D0E5697425","name":"Eliminating turbulence in oil pipelines","grant_number":"737549","call_identifier":"H2020"},{"name":"Experimental studies of the turbulence transition and transport processes in turbulent Taylor-Couette currents","grant_number":"HO 4393/1-2","_id":"25136C54-B435-11E9-9278-68D0E5697425"}],"corr_author":"1","author":[{"last_name":"Scarselli","id":"40315C30-F248-11E8-B48F-1D18A9856A87","first_name":"Davide","orcid":"0000-0001-5227-4271","full_name":"Scarselli, Davide"}],"alternative_title":["ISTA Thesis"],"publisher":"Institute of Science and Technology Austria","department":[{"_id":"BjHo"}],"status":"public","has_accepted_license":"1","oa":1},{"year":"2019","date_updated":"2023-08-25T10:16:11Z","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","_id":"5878","publication_identifier":{"eissn":["1089-7682"],"issn":["1054-1500"]},"month":"01","intvolume":"        29","publication":"Chaos: An Interdisciplinary Journal of Nonlinear Science","language":[{"iso":"eng"}],"quality_controlled":"1","citation":{"apa":"Budanur, N. B., &#38; Fleury, M. (2019). State space geometry of the chaotic pilot-wave hydrodynamics. <i>Chaos: An Interdisciplinary Journal of Nonlinear Science</i>. AIP Publishing. <a href=\"https://doi.org/10.1063/1.5058279\">https://doi.org/10.1063/1.5058279</a>","ista":"Budanur NB, Fleury M. 2019. State space geometry of the chaotic pilot-wave hydrodynamics. Chaos: An Interdisciplinary Journal of Nonlinear Science. 29(1), 013122.","ieee":"N. B. Budanur and M. Fleury, “State space geometry of the chaotic pilot-wave hydrodynamics,” <i>Chaos: An Interdisciplinary Journal of Nonlinear Science</i>, vol. 29, no. 1. AIP Publishing, 2019.","chicago":"Budanur, Nazmi B, and Marc Fleury. “State Space Geometry of the Chaotic Pilot-Wave Hydrodynamics.” <i>Chaos: An Interdisciplinary Journal of Nonlinear Science</i>. AIP Publishing, 2019. <a href=\"https://doi.org/10.1063/1.5058279\">https://doi.org/10.1063/1.5058279</a>.","mla":"Budanur, Nazmi B., and Marc Fleury. “State Space Geometry of the Chaotic Pilot-Wave Hydrodynamics.” <i>Chaos: An Interdisciplinary Journal of Nonlinear Science</i>, vol. 29, no. 1, 013122, AIP Publishing, 2019, doi:<a href=\"https://doi.org/10.1063/1.5058279\">10.1063/1.5058279</a>.","ama":"Budanur NB, Fleury M. State space geometry of the chaotic pilot-wave hydrodynamics. <i>Chaos: An Interdisciplinary Journal of Nonlinear Science</i>. 2019;29(1). doi:<a href=\"https://doi.org/10.1063/1.5058279\">10.1063/1.5058279</a>","short":"N.B. Budanur, M. Fleury, Chaos: An Interdisciplinary Journal of Nonlinear Science 29 (2019)."},"type":"journal_article","volume":29,"day":"22","date_published":"2019-01-22T00:00:00Z","article_number":"013122","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1812.09011"}],"doi":"10.1063/1.5058279","oa":1,"scopus_import":"1","status":"public","isi":1,"department":[{"_id":"BjHo"}],"publisher":"AIP Publishing","author":[{"orcid":"0000-0003-0423-5010","full_name":"Budanur, Nazmi B","last_name":"Budanur","id":"3EA1010E-F248-11E8-B48F-1D18A9856A87","first_name":"Nazmi B"},{"full_name":"Fleury, Marc","last_name":"Fleury","first_name":"Marc"}],"article_type":"original","external_id":{"arxiv":["1812.09011"],"isi":["000457409100028"]},"abstract":[{"lang":"eng","text":"We consider the motion of a droplet bouncing on a vibrating bath of the same fluid in the presence of a central potential. We formulate a rotation symmetry-reduced description of this system, which allows for the straightforward application of dynamical systems theory tools. As an illustration of the utility of the symmetry reduction, we apply it to a model of the pilot-wave system with a central harmonic force. We begin our analysis by identifying local bifurcations and the onset of chaos. We then describe the emergence of chaotic regions and their merging bifurcations, which lead to the formation of a global attractor. In this final regime, the droplet’s angular momentum spontaneously changes its sign as observed in the experiments of Perrard et al."}],"article_processing_charge":"No","title":"State space geometry of the chaotic pilot-wave hydrodynamics","arxiv":1,"publication_status":"published","related_material":{"link":[{"url":"https://aip.scitation.org/doi/abs/10.1063/1.5097157","relation":"erratum"}]},"oa_version":"Preprint","date_created":"2019-01-23T08:35:09Z","issue":"1"},{"external_id":{"arxiv":["1902.07931"],"isi":["000526029100016"]},"abstract":[{"text":"The hairpin instability of a jet in a crossflow (JICF) for a low jet-to-crossflow velocity ratio is investigated experimentally for a velocity ratio range of R ∈ (0.14, 0.75) and crossflow Reynolds numbers ReD ∈ (260, 640). From spectral analysis we characterize the Strouhal number and amplitude of the hairpin instability as a function of R and ReD. We demonstrate that the dynamics of the hairpins is well described by the Landau model, and, hence, that the instability occurs through Hopf bifurcation, similarly to other hydrodynamical oscillators such as wake behind different bluff bodies. Using the Landau model, we determine the precise threshold values of hairpin shedding. We also study the spatial dependence of this hydrodynamical instability, which shows a global behaviour.","lang":"eng"}],"page":"386-406","article_type":"original","oa_version":"Preprint","publication_status":"published","date_created":"2019-02-10T22:59:15Z","article_processing_charge":"No","title":"Experiments on a jet in a crossflow in the low-velocity-ratio regime","arxiv":1,"status":"public","oa":1,"scopus_import":"1","project":[{"name":"ISTplus - Postdoctoral Fellowships","grant_number":"754411","call_identifier":"H2020","_id":"260C2330-B435-11E9-9278-68D0E5697425"}],"author":[{"full_name":"Klotz, Lukasz","orcid":"0000-0003-1740-7635","first_name":"Lukasz","id":"2C9AF1C2-F248-11E8-B48F-1D18A9856A87","last_name":"Klotz"},{"full_name":"Gumowski, Konrad","last_name":"Gumowski","first_name":"Konrad"},{"last_name":"Wesfreid","first_name":"José Eduardo","full_name":"Wesfreid, José Eduardo"}],"department":[{"_id":"BjHo"}],"publisher":"Cambridge University Press","isi":1,"volume":863,"citation":{"ieee":"L. Klotz, K. Gumowski, and J. E. Wesfreid, “Experiments on a jet in a crossflow in the low-velocity-ratio regime,” <i>Journal of Fluid Mechanics</i>, vol. 863. Cambridge University Press, pp. 386–406, 2019.","chicago":"Klotz, Lukasz, Konrad Gumowski, and José Eduardo Wesfreid. “Experiments on a Jet in a Crossflow in the Low-Velocity-Ratio Regime.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2019. <a href=\"https://doi.org/10.1017/jfm.2018.974\">https://doi.org/10.1017/jfm.2018.974</a>.","mla":"Klotz, Lukasz, et al. “Experiments on a Jet in a Crossflow in the Low-Velocity-Ratio Regime.” <i>Journal of Fluid Mechanics</i>, vol. 863, Cambridge University Press, 2019, pp. 386–406, doi:<a href=\"https://doi.org/10.1017/jfm.2018.974\">10.1017/jfm.2018.974</a>.","short":"L. Klotz, K. Gumowski, J.E. Wesfreid, Journal of Fluid Mechanics 863 (2019) 386–406.","ama":"Klotz L, Gumowski K, Wesfreid JE. Experiments on a jet in a crossflow in the low-velocity-ratio regime. <i>Journal of Fluid Mechanics</i>. 2019;863:386-406. doi:<a href=\"https://doi.org/10.1017/jfm.2018.974\">10.1017/jfm.2018.974</a>","apa":"Klotz, L., Gumowski, K., &#38; Wesfreid, J. E. (2019). Experiments on a jet in a crossflow in the low-velocity-ratio regime. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2018.974\">https://doi.org/10.1017/jfm.2018.974</a>","ista":"Klotz L, Gumowski K, Wesfreid JE. 2019. Experiments on a jet in a crossflow in the low-velocity-ratio regime. Journal of Fluid Mechanics. 863, 386–406."},"type":"journal_article","language":[{"iso":"eng"}],"quality_controlled":"1","intvolume":"       863","publication":"Journal of Fluid Mechanics","doi":"10.1017/jfm.2018.974","date_published":"2019-03-25T00:00:00Z","main_file_link":[{"url":"https://arxiv.org/abs/1902.07931","open_access":"1"}],"day":"25","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","_id":"5943","date_updated":"2025-04-14T07:43:59Z","year":"2019","month":"03","ec_funded":1},{"isi":1,"department":[{"_id":"BjHo"}],"publisher":"Springer Nature","project":[{"_id":"260C2330-B435-11E9-9278-68D0E5697425","grant_number":"754411","name":"ISTplus - Postdoctoral Fellowships","call_identifier":"H2020"}],"corr_author":"1","author":[{"full_name":"Varshney, Atul","orcid":"0000-0002-3072-5999","last_name":"Varshney","id":"2A2006B2-F248-11E8-B48F-1D18A9856A87","first_name":"Atul"},{"full_name":"Steinberg, Victor","last_name":"Steinberg","first_name":"Victor"}],"tmp":{"short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"oa":1,"scopus_import":"1","status":"public","has_accepted_license":"1","article_processing_charge":"No","title":"Elastic alfven waves in elastic turbulence","arxiv":1,"oa_version":"Published Version","publication_status":"published","date_created":"2019-02-15T07:10:46Z","article_type":"original","file_date_updated":"2020-07-14T12:47:17Z","external_id":{"pmid":["30737403"],"isi":["000458175300001"],"arxiv":["1902.03763"]},"abstract":[{"lang":"eng","text":"Speed of sound waves in gases and liquids are governed by the compressibility of the medium. There exists another type of non-dispersive wave where the wave speed depends on stress instead of elasticity of the medium. A well-known example is the Alfven wave, which propagates through plasma permeated by a magnetic field with the speed determined by magnetic tension. An elastic analogue of Alfven waves has been predicted in a flow of dilute polymer solution where the elastic stress of the stretching polymers determines the elastic wave speed. Here we present quantitative evidence of elastic Alfven waves in elastic turbulence of a viscoelastic creeping flow between two obstacles in channel flow. The key finding in the experimental proof is a nonlinear dependence of the elastic wave speed cel on the Weissenberg number Wi, which deviates from predictions based on a model of linear polymer elasticity."}],"pmid":1,"file":[{"file_size":1331490,"file_id":"6015","date_updated":"2020-07-14T12:47:17Z","checksum":"d3acf07eaad95ec040d8e8565fc9ac37","access_level":"open_access","date_created":"2019-02-15T07:15:00Z","relation":"main_file","content_type":"application/pdf","file_name":"2019_NatureComm_Varshney.pdf","creator":"dernst"}],"publication_identifier":{"issn":["2041-1723"]},"ec_funded":1,"month":"02","year":"2019","date_updated":"2025-04-14T07:43:46Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","_id":"6014","day":"08","article_number":"652","date_published":"2019-02-08T00:00:00Z","doi":"10.1038/s41467-019-08551-0","intvolume":"        10","publication":"Nature Communications","language":[{"iso":"eng"}],"quality_controlled":"1","type":"journal_article","citation":{"chicago":"Varshney, Atul, and Victor Steinberg. “Elastic Alfven Waves in Elastic Turbulence.” <i>Nature Communications</i>. Springer Nature, 2019. <a href=\"https://doi.org/10.1038/s41467-019-08551-0\">https://doi.org/10.1038/s41467-019-08551-0</a>.","mla":"Varshney, Atul, and Victor Steinberg. “Elastic Alfven Waves in Elastic Turbulence.” <i>Nature Communications</i>, vol. 10, 652, Springer Nature, 2019, doi:<a href=\"https://doi.org/10.1038/s41467-019-08551-0\">10.1038/s41467-019-08551-0</a>.","short":"A. Varshney, V. Steinberg, Nature Communications 10 (2019).","ama":"Varshney A, Steinberg V. Elastic alfven waves in elastic turbulence. <i>Nature Communications</i>. 2019;10. doi:<a href=\"https://doi.org/10.1038/s41467-019-08551-0\">10.1038/s41467-019-08551-0</a>","ieee":"A. Varshney and V. Steinberg, “Elastic alfven waves in elastic turbulence,” <i>Nature Communications</i>, vol. 10. Springer Nature, 2019.","ista":"Varshney A, Steinberg V. 2019. Elastic alfven waves in elastic turbulence. Nature Communications. 10, 652.","apa":"Varshney, A., &#38; Steinberg, V. (2019). Elastic alfven waves in elastic turbulence. <i>Nature Communications</i>. Springer Nature. <a href=\"https://doi.org/10.1038/s41467-019-08551-0\">https://doi.org/10.1038/s41467-019-08551-0</a>"},"ddc":["530"],"volume":10},{"publication_identifier":{"issn":["2041-1723"]},"ec_funded":1,"month":"02","year":"2019","date_updated":"2025-04-14T07:44:00Z","user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","_id":"6069","day":"26","article_number":"937","date_published":"2019-02-26T00:00:00Z","doi":"10.1038/s41467-019-08916-5","intvolume":"        10","publication":"Nature Communications","language":[{"iso":"eng"}],"quality_controlled":"1","citation":{"ista":"Mayzel J, Steinberg V, Varshney A. 2019. Stokes flow analogous to viscous electron current in graphene. Nature Communications. 10, 937.","apa":"Mayzel, J., Steinberg, V., &#38; Varshney, A. (2019). Stokes flow analogous to viscous electron current in graphene. <i>Nature Communications</i>. Springer Nature. <a href=\"https://doi.org/10.1038/s41467-019-08916-5\">https://doi.org/10.1038/s41467-019-08916-5</a>","ama":"Mayzel J, Steinberg V, Varshney A. Stokes flow analogous to viscous electron current in graphene. <i>Nature Communications</i>. 2019;10. doi:<a href=\"https://doi.org/10.1038/s41467-019-08916-5\">10.1038/s41467-019-08916-5</a>","short":"J. Mayzel, V. Steinberg, A. Varshney, Nature Communications 10 (2019).","mla":"Mayzel, Jonathan, et al. “Stokes Flow Analogous to Viscous Electron Current in Graphene.” <i>Nature Communications</i>, vol. 10, 937, Springer Nature, 2019, doi:<a href=\"https://doi.org/10.1038/s41467-019-08916-5\">10.1038/s41467-019-08916-5</a>.","chicago":"Mayzel, Jonathan, Victor Steinberg, and Atul Varshney. “Stokes Flow Analogous to Viscous Electron Current in Graphene.” <i>Nature Communications</i>. Springer Nature, 2019. <a href=\"https://doi.org/10.1038/s41467-019-08916-5\">https://doi.org/10.1038/s41467-019-08916-5</a>.","ieee":"J. Mayzel, V. Steinberg, and A. Varshney, “Stokes flow analogous to viscous electron current in graphene,” <i>Nature Communications</i>, vol. 10. Springer Nature, 2019."},"type":"journal_article","ddc":["530","532"],"volume":10,"isi":1,"publisher":"Springer Nature","department":[{"_id":"BjHo"}],"project":[{"call_identifier":"H2020","name":"ISTplus - Postdoctoral Fellowships","grant_number":"754411","_id":"260C2330-B435-11E9-9278-68D0E5697425"}],"corr_author":"1","author":[{"first_name":"Jonathan","last_name":"Mayzel","full_name":"Mayzel, Jonathan"},{"full_name":"Steinberg, Victor","last_name":"Steinberg","first_name":"Victor"},{"id":"2A2006B2-F248-11E8-B48F-1D18A9856A87","first_name":"Atul","last_name":"Varshney","full_name":"Varshney, Atul","orcid":"0000-0002-3072-5999"}],"tmp":{"short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"oa":1,"scopus_import":"1","status":"public","has_accepted_license":"1","title":"Stokes flow analogous to viscous electron current in graphene","article_processing_charge":"No","date_created":"2019-03-05T13:18:30Z","oa_version":"Published Version","publication_status":"published","file_date_updated":"2020-07-14T12:47:18Z","external_id":{"isi":["000459704600001"]},"abstract":[{"text":"Electron transport in two-dimensional conducting materials such as graphene, with dominant electron–electron interaction, exhibits unusual vortex flow that leads to a nonlocal current-field relation (negative resistance), distinct from the classical Ohm’s law. The transport behavior of these materials is best described by low Reynolds number hydrodynamics, where the constitutive pressure–speed relation is Stoke’s law. Here we report evidence of such vortices observed in a viscous flow of Newtonian fluid in a microfluidic device consisting of a rectangular cavity—analogous to the electronic system. We extend our experimental observations to elliptic cavities of different eccentricities, and validate them by numerically solving bi-harmonic equation obtained for the viscous flow with no-slip boundary conditions. We verify the existence of a  predicted threshold at which vortices appear. Strikingly, we find that a two-dimensional theoretical model captures the essential features of three-dimensional Stokes flow in experiments.","lang":"eng"}],"file":[{"date_created":"2019-03-05T13:33:04Z","access_level":"open_access","checksum":"61192fc49e0d44907c2a4fe384e4b97f","creator":"dernst","content_type":"application/pdf","file_name":"2019_NatureComm_Mayzel.pdf","relation":"main_file","file_id":"6070","file_size":2646391,"date_updated":"2020-07-14T12:47:18Z"}]},{"oa":1,"scopus_import":"1","status":"public","department":[{"_id":"BjHo"}],"publisher":"Elsevier","isi":1,"author":[{"first_name":"Baofang","last_name":"Song","full_name":"Song, Baofang"},{"full_name":"Plana, Carlos","last_name":"Plana","first_name":"Carlos"},{"first_name":"Jose M","id":"40770848-F248-11E8-B48F-1D18A9856A87","last_name":"Lopez Alonso","orcid":"0000-0002-0384-2022","full_name":"Lopez Alonso, Jose M"},{"first_name":"Marc","last_name":"Avila","full_name":"Avila, Marc"}],"article_type":"original","external_id":{"arxiv":["1902.07351"],"isi":["000474496000002"]},"abstract":[{"text":"Phase-field methods have long been used to model the flow of immiscible fluids. Their ability to naturally capture interface topological changes is widely recognized, but their accuracy in simulating flows of real fluids in practical geometries is not established. We here quantitatively investigate the convergence of the phase-field method to the sharp-interface limit with simulations of two-phase pipe flow. We focus on core-annular flows, in which a highly viscous fluid is lubricated by a less viscous fluid, and validate our simulations with an analytic laminar solution, a formal linear stability analysis and also in the fully nonlinear regime. We demonstrate the ability of the phase-field method to accurately deal with non-rectangular geometry, strong advection, unsteady fluctuations and large viscosity contrast. We argue that phase-field methods are very promising for quantitatively studying moderately turbulent flows, especially at high concentrations of the disperse phase.","lang":"eng"}],"page":"14-24","date_created":"2019-05-13T07:58:35Z","publication_status":"published","oa_version":"Preprint","article_processing_charge":"No","title":"Phase-field simulation of core-annular pipe flow","arxiv":1,"year":"2019","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","_id":"6413","date_updated":"2026-04-16T09:49:27Z","publication_identifier":{"issn":["0301-9322"]},"month":"08","language":[{"iso":"eng"}],"quality_controlled":"1","intvolume":"       117","publication":"International Journal of Multiphase Flow","volume":117,"type":"journal_article","citation":{"ista":"Song B, Plana C, Lopez Alonso JM, Avila M. 2019. Phase-field simulation of core-annular pipe flow. International Journal of Multiphase Flow. 117, 14–24.","apa":"Song, B., Plana, C., Lopez Alonso, J. M., &#38; Avila, M. (2019). Phase-field simulation of core-annular pipe flow. <i>International Journal of Multiphase Flow</i>. Elsevier. <a href=\"https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027\">https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027</a>","short":"B. Song, C. Plana, J.M. Lopez Alonso, M. Avila, International Journal of Multiphase Flow 117 (2019) 14–24.","ama":"Song B, Plana C, Lopez Alonso JM, Avila M. Phase-field simulation of core-annular pipe flow. <i>International Journal of Multiphase Flow</i>. 2019;117:14-24. doi:<a href=\"https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027\">10.1016/j.ijmultiphaseflow.2019.04.027</a>","chicago":"Song, Baofang, Carlos Plana, Jose M Lopez Alonso, and Marc Avila. “Phase-Field Simulation of Core-Annular Pipe Flow.” <i>International Journal of Multiphase Flow</i>. Elsevier, 2019. <a href=\"https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027\">https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027</a>.","mla":"Song, Baofang, et al. “Phase-Field Simulation of Core-Annular Pipe Flow.” <i>International Journal of Multiphase Flow</i>, vol. 117, Elsevier, 2019, pp. 14–24, doi:<a href=\"https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027\">10.1016/j.ijmultiphaseflow.2019.04.027</a>.","ieee":"B. Song, C. Plana, J. M. Lopez Alonso, and M. Avila, “Phase-field simulation of core-annular pipe flow,” <i>International Journal of Multiphase Flow</i>, vol. 117. Elsevier, pp. 14–24, 2019."},"date_published":"2019-08-01T00:00:00Z","main_file_link":[{"url":"https://arxiv.org/abs/1902.07351","open_access":"1"}],"day":"01","doi":"10.1016/j.ijmultiphaseflow.2019.04.027"},{"year":"2019","date_updated":"2025-04-15T06:50:28Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","_id":"6779","publication_identifier":{"eissn":["2470-0053"],"issn":["2470-0045"]},"ec_funded":1,"month":"07","intvolume":"       100","publication":"Physical Review E","language":[{"iso":"eng"}],"quality_controlled":"1","type":"journal_article","citation":{"ieee":"B. Suri, R. K. Pallantla, M. F. Schatz, and R. O. Grigoriev, “Heteroclinic and homoclinic connections in a Kolmogorov-like flow,” <i>Physical Review E</i>, vol. 100, no. 1. American Physical Society, 2019.","short":"B. Suri, R.K. Pallantla, M.F. Schatz, R.O. Grigoriev, Physical Review E 100 (2019).","ama":"Suri B, Pallantla RK, Schatz MF, Grigoriev RO. Heteroclinic and homoclinic connections in a Kolmogorov-like flow. <i>Physical Review E</i>. 2019;100(1). doi:<a href=\"https://doi.org/10.1103/physreve.100.013112\">10.1103/physreve.100.013112</a>","chicago":"Suri, Balachandra, Ravi Kumar Pallantla, Michael F. Schatz, and Roman O. Grigoriev. “Heteroclinic and Homoclinic Connections in a Kolmogorov-like Flow.” <i>Physical Review E</i>. American Physical Society, 2019. <a href=\"https://doi.org/10.1103/physreve.100.013112\">https://doi.org/10.1103/physreve.100.013112</a>.","mla":"Suri, Balachandra, et al. “Heteroclinic and Homoclinic Connections in a Kolmogorov-like Flow.” <i>Physical Review E</i>, vol. 100, no. 1, 013112, American Physical Society, 2019, doi:<a href=\"https://doi.org/10.1103/physreve.100.013112\">10.1103/physreve.100.013112</a>.","apa":"Suri, B., Pallantla, R. K., Schatz, M. F., &#38; Grigoriev, R. O. (2019). Heteroclinic and homoclinic connections in a Kolmogorov-like flow. <i>Physical Review E</i>. American Physical Society. <a href=\"https://doi.org/10.1103/physreve.100.013112\">https://doi.org/10.1103/physreve.100.013112</a>","ista":"Suri B, Pallantla RK, Schatz MF, Grigoriev RO. 2019. Heteroclinic and homoclinic connections in a Kolmogorov-like flow. Physical Review E. 100(1), 013112."},"ddc":["532"],"volume":100,"day":"25","article_number":"013112","date_published":"2019-07-25T00:00:00Z","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1907.05860"}],"doi":"10.1103/physreve.100.013112","oa":1,"scopus_import":"1","status":"public","isi":1,"department":[{"_id":"BjHo"}],"publisher":"American Physical Society","project":[{"call_identifier":"FP7","name":"International IST Postdoc Fellowship Programme","grant_number":"291734","_id":"25681D80-B435-11E9-9278-68D0E5697425"}],"author":[{"full_name":"Suri, Balachandra","last_name":"Suri","first_name":"Balachandra","id":"47A5E706-F248-11E8-B48F-1D18A9856A87"},{"full_name":"Pallantla, Ravi Kumar","last_name":"Pallantla","first_name":"Ravi Kumar"},{"last_name":"Schatz","first_name":"Michael F.","full_name":"Schatz, Michael F."},{"full_name":"Grigoriev, Roman O.","last_name":"Grigoriev","first_name":"Roman O."}],"article_type":"original","external_id":{"arxiv":["1907.05860"],"isi":["000477911800012"]},"abstract":[{"text":"Recent studies suggest that unstable recurrent solutions of the Navier-Stokes equation provide new insights\r\ninto dynamics of turbulent flows. In this study, we compute an extensive network of dynamical connections\r\nbetween such solutions in a weakly turbulent quasi-two-dimensional Kolmogorov flow that lies in the inversion symmetric subspace. In particular, we find numerous isolated heteroclinic connections between different\r\ntypes of solutions—equilibria, periodic, and quasiperiodic orbits—as well as continua of connections forming\r\nhigher-dimensional connecting manifolds. We also compute a homoclinic connection of a periodic orbit and\r\nprovide strong evidence that the associated homoclinic tangle forms the chaotic repeller that underpins transient\r\nturbulence in the symmetric subspace.","lang":"eng"}],"article_processing_charge":"No","title":"Heteroclinic and homoclinic connections in a Kolmogorov-like flow","arxiv":1,"date_created":"2019-08-09T09:40:41Z","publication_status":"published","oa_version":"Preprint","issue":"1"},{"abstract":[{"lang":"eng","text":"In many shear flows like pipe flow, plane Couette flow, plane Poiseuille flow,  etc. turbulence emerges subcritically. Here, when subjected to strong enough perturbations, the flow becomes turbulent in spite of the laminar base flow being linearly stable.  The nature of this instability has puzzled the scientific community for decades. At onset, turbulence appears in localized patches and flows are spatio-temporally intermittent.  In pipe flow the localized turbulent structures are referred to as puffs and in planar flows like plane Couette and channel flow, patches arise in the form of localized oblique bands. In this thesis, we study the onset of turbulence in channel flow in direct numerical simulations from a dynamical system theory perspective, as well as by performing experiments in a large aspect ratio channel.\r\n\r\nThe aim of the experimental work is to determine the critical Reynolds number where turbulence first becomes sustained. Recently, the onset of turbulence has been described in analogy to absorbing state phase transition (i.e. directed percolation). In particular, it has been shown that the critical point can be estimated from the competition between spreading and decay processes. Here, by performing experiments, we identify the mechanisms underlying turbulence proliferation in channel flow and find the critical Reynolds number, above which turbulence becomes sustained. Above the critical point, the continuous growth at the tip of the stripes outweighs the stochastic shedding of turbulent patches at the tail and the stripes expand. For growing stripes, the probability to decay decreases while the probability of stripe splitting increases. Consequently, and unlike for the puffs in pipe flow, neither of these two processes is time-independent i.e. memoryless. Coupling between stripe expansion and creation of new stripes via splitting leads to a significantly lower critical point ($Re_c=670+/-10$) than most earlier studies suggest.  \r\n\r\nWhile the above approach sheds light on how turbulence first becomes sustained, it provides no insight into the origin of the stripes themselves. In the numerical part of the thesis we investigate how turbulent stripes form from invariant solutions of the Navier-Stokes equations. The origin of these turbulent stripes can be identified by applying concepts from the dynamical system theory. In doing so, we identify the exact coherent structures underlying stripes and their bifurcations and how they give rise to the turbulent attractor in phase space. We first report a family of localized nonlinear traveling wave solutions of the Navier-Stokes equations in channel flow. These solutions show structural similarities with turbulent stripes in experiments like obliqueness, quasi-streamwise streaks and vortices, etc. A parametric study of these traveling wave solution is performed, with parameters like Reynolds number, stripe tilt angle and domain size, including the stability of the solutions. These solutions emerge through saddle-node bifurcations and form a phase space skeleton for the turbulent stripes observed in the experiments. The lower branches of these TW solutions at different tilt angles undergo Hopf bifurcation and new solutions branches of relative periodic orbits emerge. These RPO solutions do not belong to the same family and therefore the routes to chaos for different angles are different.  \r\n\r\nIn shear flows, turbulence at onset is transient in nature.  Consequently,turbulence can not be tracked to lower Reynolds numbers, where the dynamics may simplify. Before this happens, turbulence becomes short-lived and laminarizes. In the last part of the thesis, we show that using numerical simulations we can continue turbulent stripes in channel flow past the 'relaminarization barrier' all the way to their origin. Here, turbulent stripe dynamics simplifies and the fluctuations are no longer stochastic and the stripe settles down to a relative periodic orbit. This relative periodic orbit originates from the aforementioned traveling wave solutions. Starting from the relative periodic orbit, a small increase in speed i.e. Reynolds number gives rise to chaos and the attractor dimension sharply increases in contrast to the classical transition scenario where the instabilities affect the flow globally and give rise to much more gradual route to turbulence."}],"page":"138","file":[{"relation":"source_file","content_type":"application/zip","file_name":"Chaitanya_Paranjape_source_files_tex_figures.zip","creator":"cparanjape","access_level":"closed","date_created":"2019-10-23T09:54:43Z","checksum":"7ba298ba0ce7e1d11691af6b8eaf0a0a","date_updated":"2020-07-14T12:47:46Z","file_id":"6962","file_size":45828099},{"checksum":"642697618314e31ac31392da7909c2d9","date_created":"2019-10-23T10:37:09Z","access_level":"open_access","creator":"cparanjape","relation":"main_file","file_name":"Chaitanya_Paranjape_Thesis.pdf","content_type":"application/pdf","file_size":19504197,"file_id":"6963","date_updated":"2020-07-14T12:47:46Z"}],"file_date_updated":"2020-07-14T12:47:46Z","degree_awarded":"PhD","keyword":["Instabilities","Turbulence","Nonlinear dynamics"],"title":"Onset of turbulence in plane Poiseuille flow","article_processing_charge":"No","oa_version":"Published Version","date_created":"2019-10-22T12:08:43Z","publication_status":"published","has_accepted_license":"1","status":"public","oa":1,"alternative_title":["ISTA Thesis"],"corr_author":"1","author":[{"full_name":"Paranjape, Chaitanya S","id":"3D85B7C4-F248-11E8-B48F-1D18A9856A87","first_name":"Chaitanya S","last_name":"Paranjape"}],"department":[{"_id":"BjHo"}],"publisher":"Institute of Science and Technology Austria","type":"dissertation","citation":{"ista":"Paranjape CS. 2019. Onset of turbulence in plane Poiseuille flow. Institute of Science and Technology Austria.","apa":"Paranjape, C. S. (2019). <i>Onset of turbulence in plane Poiseuille flow</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:6957\">https://doi.org/10.15479/AT:ISTA:6957</a>","short":"C.S. Paranjape, Onset of Turbulence in Plane Poiseuille Flow, Institute of Science and Technology Austria, 2019.","ama":"Paranjape CS. Onset of turbulence in plane Poiseuille flow. 2019. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:6957\">10.15479/AT:ISTA:6957</a>","mla":"Paranjape, Chaitanya S. <i>Onset of Turbulence in Plane Poiseuille Flow</i>. Institute of Science and Technology Austria, 2019, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:6957\">10.15479/AT:ISTA:6957</a>.","chicago":"Paranjape, Chaitanya S. “Onset of Turbulence in Plane Poiseuille Flow.” Institute of Science and Technology Austria, 2019. <a href=\"https://doi.org/10.15479/AT:ISTA:6957\">https://doi.org/10.15479/AT:ISTA:6957</a>.","ieee":"C. S. Paranjape, “Onset of turbulence in plane Poiseuille flow,” Institute of Science and Technology Austria, 2019."},"ddc":["532"],"language":[{"iso":"eng"}],"doi":"10.15479/AT:ISTA:6957","day":"24","date_published":"2019-10-24T00:00:00Z","date_updated":"2026-04-08T07:46:58Z","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","_id":"6957","supervisor":[{"full_name":"Hof, Björn","orcid":"0000-0003-2057-2754","id":"3A374330-F248-11E8-B48F-1D18A9856A87","first_name":"Björn","last_name":"Hof"}],"OA_place":"publisher","year":"2019","month":"10","publication_identifier":{"eissn":["2663-337X"]}}]