[{"publisher":"Cambridge University Press","citation":{"apa":"Marensi, E., Yalniz, G., &#38; Hof, B. (2023). Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2023.780\">https://doi.org/10.1017/jfm.2023.780</a>","ieee":"E. Marensi, G. Yalniz, and B. Hof, “Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows,” <i>Journal of Fluid Mechanics</i>, vol. 974. Cambridge University Press, 2023.","ama":"Marensi E, Yalniz G, Hof B. Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows. <i>Journal of Fluid Mechanics</i>. 2023;974. doi:<a href=\"https://doi.org/10.1017/jfm.2023.780\">10.1017/jfm.2023.780</a>","chicago":"Marensi, Elena, Gökhan Yalniz, and Björn Hof. “Dynamics and Proliferation of Turbulent Stripes in Plane-Poiseuille and Plane-Couette Flows.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2023. <a href=\"https://doi.org/10.1017/jfm.2023.780\">https://doi.org/10.1017/jfm.2023.780</a>.","mla":"Marensi, Elena, et al. “Dynamics and Proliferation of Turbulent Stripes in Plane-Poiseuille and Plane-Couette Flows.” <i>Journal of Fluid Mechanics</i>, vol. 974, A21, Cambridge University Press, 2023, doi:<a href=\"https://doi.org/10.1017/jfm.2023.780\">10.1017/jfm.2023.780</a>.","short":"E. Marensi, G. Yalniz, B. Hof, Journal of Fluid Mechanics 974 (2023).","ista":"Marensi E, Yalniz G, Hof B. 2023. Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows. Journal of Fluid Mechanics. 974, A21."},"department":[{"_id":"GradSch"},{"_id":"BjHo"}],"date_created":"2023-10-30T09:32:28Z","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"status":"public","month":"11","date_published":"2023-11-10T00:00:00Z","quality_controlled":"1","project":[{"grant_number":"662960","name":"Revisiting the Turbulence Problem Using Statistical Mechanics","_id":"238598C6-32DE-11EA-91FC-C7463DDC885E"}],"intvolume":"       974","publication_identifier":{"issn":["0022-1120"],"eissn":["1469-7645"]},"_id":"14466","author":[{"id":"0BE7553A-1004-11EA-B805-18983DDC885E","orcid":"0000-0001-7173-4923","full_name":"Marensi, Elena","last_name":"Marensi","first_name":"Elena"},{"full_name":"Yalniz, Gökhan","orcid":"0000-0002-8490-9312","id":"66E74FA2-D8BF-11E9-8249-8DE2E5697425","first_name":"Gökhan","last_name":"Yalniz"},{"first_name":"Björn","last_name":"Hof","full_name":"Hof, Björn","orcid":"0000-0003-2057-2754","id":"3A374330-F248-11E8-B48F-1D18A9856A87"}],"arxiv":1,"external_id":{"arxiv":["2212.12406"],"isi":["001088363700001"]},"isi":1,"related_material":{"record":[{"status":"public","id":"19684","relation":"dissertation_contains"}]},"oa_version":"Published Version","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","has_accepted_license":"1","acknowledgement":"E.M. acknowledges funding from the ISTplus fellowship programme. G.Y. and B.H. acknowledge a grant from the Simons Foundation (662960, BH).","file":[{"file_name":"2023_JourFluidMechanics_Marensi.pdf","file_size":2804641,"checksum":"17c64c1fb0d5f73252364bf98b0b9e1a","success":1,"access_level":"open_access","relation":"main_file","date_created":"2024-02-15T09:05:21Z","content_type":"application/pdf","creator":"dernst","date_updated":"2024-02-15T09:05:21Z","file_id":"14996"}],"keyword":["turbulence","transition to turbulence","patterns"],"article_type":"original","article_processing_charge":"Yes (via OA deal)","date_updated":"2026-04-07T11:47:05Z","publication":"Journal of Fluid Mechanics","type":"journal_article","ddc":["530"],"scopus_import":"1","file_date_updated":"2024-02-15T09:05:21Z","publication_status":"published","doi":"10.1017/jfm.2023.780","volume":974,"title":"Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows","year":"2023","day":"10","oa":1,"corr_author":"1","abstract":[{"lang":"eng","text":"The first long-lived turbulent structures observable in planar shear flows take the form of localized stripes, inclined with respect to the mean flow direction. The dynamics of these stripes is central to transition, and recent studies proposed an analogy to directed percolation where the stripes’ proliferation is ultimately responsible for the turbulence becoming sustained. In the present study we focus on the internal stripe dynamics as well as on the eventual stripe expansion, and we compare the underlying mechanisms in pressure- and shear-driven planar flows, respectively, plane-Poiseuille and plane-Couette flow. Despite the similarities of the overall laminar–turbulence patterns, the stripe proliferation processes in the two cases are fundamentally different. Starting from the growth and sustenance of individual stripes, we find that in plane-Couette flow new streaks are created stochastically throughout the stripe whereas in plane-Poiseuille flow streak creation is deterministic and occurs locally at the downstream tip. Because of the up/downstream symmetry, Couette stripes, in contrast to Poiseuille stripes, have two weak and two strong laminar turbulent interfaces. These differences in symmetry as well as in internal growth give rise to two fundamentally different stripe splitting mechanisms. In plane-Poiseuille flow splitting is connected to the elongational growth of the original stripe, and it results from a break-off/shedding of the stripe's tail. In plane-Couette flow splitting follows from a broadening of the original stripe and a division along the stripe into two slimmer stripes."}],"language":[{"iso":"eng"}],"article_number":"A21"},{"author":[{"full_name":"Agrawal, Nishchal","id":"469E6004-F248-11E8-B48F-1D18A9856A87","first_name":"Nishchal","last_name":"Agrawal"}],"OA_place":"publisher","related_material":{"record":[{"status":"public","id":"6189","relation":"part_of_dissertation"}]},"oa_version":"Published Version","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","has_accepted_license":"1","file":[{"content_type":"application/x-zip-compressed","creator":"nagrawal","date_updated":"2022-07-29T22:30:05Z","file_id":"9744","embargo_to":"open_access","file_name":"Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.zip","checksum":"77436be3563a90435024307b1b5ee7e8","file_size":22859658,"access_level":"closed","relation":"source_file","date_created":"2021-07-28T13:32:02Z"},{"relation":"main_file","access_level":"open_access","date_created":"2021-07-28T13:32:05Z","checksum":"72a891d7daba85445c29b868c22575ed","file_size":18658048,"file_name":"Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.pdf","embargo":"2022-07-28","file_id":"9745","date_updated":"2022-07-29T22:30:05Z","content_type":"application/pdf","creator":"nagrawal"}],"keyword":["Drag Reduction","Transition to Turbulence","Multiphase Flows","particle Laden Flows","Complex Flows","Experiments","Fluid Dynamics"],"citation":{"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>.","ista":"Agrawal N. 2021. Transition to turbulence and drag reduction in particle-laden pipe flows. Institute of Science and Technology Austria.","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>.","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>","ieee":"N. Agrawal, “Transition to turbulence and drag reduction in particle-laden pipe flows,” Institute of Science and Technology Austria, 2021.","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>"},"publisher":"Institute of Science and Technology Austria","date_created":"2021-07-27T13:40:30Z","department":[{"_id":"GradSch"},{"_id":"BjHo"}],"page":"118","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"status":"public","month":"07","date_published":"2021-07-29T00:00:00Z","publication_identifier":{"issn":["2663-337X"]},"_id":"9728","file_date_updated":"2022-07-29T22:30:05Z","publication_status":"published","doi":"10.15479/at:ista:9728","title":"Transition to turbulence and drag reduction in particle-laden pipe flows","alternative_title":["ISTA Thesis"],"year":"2021","day":"29","oa":1,"acknowledged_ssus":[{"_id":"M-Shop"}],"supervisor":[{"last_name":"Hof","first_name":"Björn","full_name":"Hof, Björn","orcid":"0000-0003-2057-2754","id":"3A374330-F248-11E8-B48F-1D18A9856A87"}],"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."}],"corr_author":"1","language":[{"iso":"eng"}],"article_processing_charge":"No","date_updated":"2026-04-16T08:43:20Z","type":"dissertation","ddc":["532"],"degree_awarded":"PhD"}]