@article{14377,
  abstract     = {Coherent flows of self-propelled particles are characterized by vortices and jets that sustain chaotic flows, referred to as active turbulence. Here, we reveal a crossover between defect-free active turbulence and active turbulence laden with topological defects. Interestingly, we show that concurrent to the crossover from defect-free to defect-laden active turbulence is the restoration of the previously broken SO(2) symmetry signaled by the fast decay of the two-point correlations. By stability analyses of the topological charge density field, we provide theoretical insights on the criterion for the crossover to the defect-laden active turbulent state. Despite the distinct symmetry features between these two active turbulence regimes, the flow fluctuations exhibit universal statistical scaling behaviors at large scales, while the spectrum of polarity fluctuations decays exponentially at small length scales compared to the active energy injection length. These findings reveal a dynamical crossover between distinct spatiotemporal organization patterns in polar active matter.},
  author       = {Andersen, Benjamin H. and Renaud, Julian B and Rønning, Jonas and Angheluta, Luiza and Doostmohammadi, Amin},
  issn         = {2469-990X},
  journal      = {Physical Review Fluids},
  keywords     = {Fluid Flow and Transfer Processes, Modeling and Simulation, Computational Mechanics},
  number       = {6},
  publisher    = {American Physical Society},
  title        = {{Symmetry-restoring crossover from defect-free to defect-laden turbulence in polar active matter}},
  doi          = {10.1103/physrevfluids.8.063101},
  volume       = {8},
  year         = {2023},
}

@article{12146,
  abstract     = {In this paper, we explore the stability and dynamical relevance of a wide variety of steady, time-periodic, quasiperiodic, and chaotic flows arising between orthogonally stretching parallel plates. We first explore the stability of all the steady flow solution families formerly identified by Ayats et al. [“Flows between orthogonally stretching parallel plates,” Phys. Fluids 33, 024103 (2021)], concluding that only the one that originates from the Stokesian approximation is actually stable. When both plates are shrinking at identical or nearly the same deceleration rates, this Stokesian flow exhibits a Hopf bifurcation that leads to stable time-periodic regimes. The resulting time-periodic orbits or flows are tracked for different Reynolds numbers and stretching rates while monitoring their Floquet exponents to identify secondary instabilities. It is found that these time-periodic flows also exhibit Neimark–Sacker bifurcations, generating stable quasiperiodic flows (tori) that may sometimes give rise to chaotic dynamics through a Ruelle–Takens–Newhouse scenario. However, chaotic dynamics is unusually observed, as the quasiperiodic flows generally become phase-locked through a resonance mechanism before a strange attractor may arise, thus restoring the time-periodicity of the flow. In this work, we have identified and tracked four different resonance regions, also known as Arnold tongues or horns. In particular, the 1 : 4 strong resonance region is explored in great detail, where the identified scenarios are in very good agreement with normal form theory. },
  author       = {Wang, B. and Ayats López, Roger and Meseguer, A. and Marques, F.},
  issn         = {1089-7666},
  journal      = {Physics of Fluids},
  keywords     = {Condensed Matter Physics, Fluid Flow and Transfer Processes, Mechanics of Materials, Computational Mechanics, Mechanical Engineering},
  number       = {11},
  publisher    = {AIP Publishing},
  title        = {{Phase-locking flows between orthogonally stretching parallel plates}},
  doi          = {10.1063/5.0124152},
  volume       = {34},
  year         = {2022},
}

@article{12279,
  abstract     = {We report frictional drag reduction and a complete flow relaminarization of elastic turbulence (ET) at vanishing inertia in a viscoelastic channel flow past an obstacle. We show that the intensity of the observed elastic waves and wall-normal vorticity correlate well with the measured drag above the onset of ET. Moreover, we find that the elastic wave frequency grows with the Weissenberg number, and at sufficiently high frequency it causes a decay of the elastic waves, resulting in ET attenuation and drag reduction. Thus, this allows us to substantiate a physical mechanism, involving the interaction of elastic waves with wall-normal vorticity fluctuations, leading to the drag reduction and relaminarization phenomena at low Reynolds number.},
  author       = {Kumar, M. Vijay and Varshney, Atul and Li, Dongyang and Steinberg, Victor},
  issn         = {2469-990X},
  journal      = {Physical Review Fluids},
  keywords     = {Fluid Flow and Transfer Processes, Modeling and Simulation, Computational Mechanics},
  number       = {8},
  publisher    = {American Physical Society},
  title        = {{Relaminarization of elastic turbulence}},
  doi          = {10.1103/physrevfluids.7.l081301},
  volume       = {7},
  year         = {2022},
}