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Author(s): Katepalli R. Sreenivasan and Victor Yakhot Turbulent flows contain occasional, well-separated sharp features, as illustrated in this picture by Bonn et al. (1993), reproduced with permission, surrounded mostly by low levels of activity. Both interacting structures contribute to the complexity of turbulence. A full theory requires the understanding of both, which is what our paper attempts to do. We predict quantitatively the multi-scaling...

Author(s): Jayanta K. Bhattacharjee and Arnab K. Ray A circular hydraulic jump is a discontinuous rise of the downstream height of a radially outflowing liquid (water). The discontinuous circular front, which can be easily seen in a kitchen sink, is a hydrodynamic white hole. When two such impenetrable white holes collide, rather than yielding any ground to each other, they force a wall of liquid to stand between themselves. We associate surface...

Author(s): Kannabiran Seshasayanan, Vassilios Dallas, and Stephan Fauve We study the primary bifurcations of a plane parallel flow in a channel with Kolmogorov forcing. We find a new type of bifurcation with both the oscillation frequency and the amplitude of the growing mode being zero at the threshold. We call this a stationary drift bifurcation. The laminar steady flow can display different types of bifurcation depending on the forcing wave...

Author(s): Xiaoxia Zhang and Heidi Nepf We develop a wave damping model based on a prediction of current- and wave-induced force on individual plants. The model captures the influence of reconfiguration on wave forces, the impact of current on wave group velocity, and the modification of in-canopy time-mean and wave orbital velocity associated with canopy drag, all of which affect the wave dissipation by vegetation. The model explains why weak...

Author(s): H. Reed Ogrosky A two-layer falling film consisting of two viscous fluids with identical density but different viscosity lining the interior of a vertical tube is studied using a long-wave asymptotic model. The impact of the viscosity ratio on the film linear stability and nonlinear dynamics are explored. It is shown that a less viscous outer layer can decrease the total film thickness required for plugs to form; the significance of...

Author(s): Zhouyang Ge, Raffaella Martone, Luca Brandt, and Mario Minale Experiments and simulations of a non-Brownian suspension of particles demonstrate that weak van der Waals (adhesive) interactions induce rate dependence of the rheological response in oscillatory shear flow, with enhanced particle diffusivities and cluster formations below a critical shear rate, even though the steady shear behavior remains rate-independent. Phase diagrams...

Author(s): Zonghao Zou, Wilson Lough, and Saverio Spagnolie A model bacterium with a flexible flagellar hook generically swims along a helical trajectory, even when incorporating detailed hydrodynamics. A bifurcation in the hook’s equilibrium bending angle below a critical bending stiffness can have a dramatic effect on the trajectory’s helical pitch angle. Analytical predictions for the bifurcation’s dependence on the hook’s spontaneous curvature...