Physical Review Fluids
Author(s): S. Lejeune and T. Gilet
Experiments on the impact of a drop near the edge of an inclined substrate are reported. A liquid sheet forms beyond the edge, then fragments into droplets. This configuration is a minimal model of the crucial raindrop impacts on plant leaves that are responsible for the dispersal of crop diseases.
[Phys. Rev. Fluids 4, 053601] Published Wed May 08, 2019
Author(s): Qiming Wang, Manman Ma, and Michael Siegel
The deformation and breakup of an axisymmetric electrolyte drop in a dielectric medium stretched by an electric field is studied. An accurate and efficient boundary integral method is developed to solve the time-dependent Stokes flow problem in the case of arbitrary Debye layer thickness.
[Phys. Rev. Fluids 4, 053702] Published Wed May 08, 2019
Author(s): Mohammadreza Momenifar, Rohit Dhariwal, and Andrew D. Bragg
Using direct numerical simulation it is shown that even when bidisperse particles are settling rapidly, intermittent fluctuations allow turbulence to continue to play a key role in their relative motion, an effect increasing with Re. Low-order statistics relevant to collision rates are found to depend only weakly on Re.
[Phys. Rev. Fluids 4, 054301] Published Wed May 08, 2019
Second-order sensitivity in the cylinder wake: Optimal spanwise-periodic wall actuation and wall deformation
Author(s): E. Boujo, A. Fani, and F. Gallaire
Two-dimensional flows can be controlled efficiently with spanwise-periodic wall forcing or wall deformation. Optimal “wavy” controls for the linear stability of the laminar flow past a cylinder are obtained with an adjoint method.
[Phys. Rev. Fluids 4, 053901] Published Tue May 07, 2019
Author(s): Wu-Yang Zhang, Wei-Xi Huang, and Chun-Xiao Xu
Numerical simulations of turbulent flows over traveling wavy boundaries reveal that very large-scale motions are enhanced by a wavy boundary, but their intensities are decreased as wave phase speed increases. The wave-induced flow provides an extra energy transfer for the very-large-scale motions.
[Phys. Rev. Fluids 4, 054601] Published Tue May 07, 2019
Author(s): Aaron Rips and Rajat Mittal
Flow-induced flutter of flexible flapping membranes can greatly increase scalar mixing in channel flows in the inertial microfluidics regime. We use flow-structure interaction simulations to investigate their flow physics and mixing ability and find rapid mixing with relatively low pressure loss.
[Phys. Rev. Fluids 4, 054501] Published Mon May 06, 2019
Author(s): Kevin Rosenberg, Sean Symon, and Beverley J. McKeon
The representation of self-sustaining processes via resolvent analysis for turbulent flows is improved where the resolvent operator is not low rank by approximating the nonlinear forcing using parasitic modes, with analogy to weakly nonlinear analysis near critical Reynolds numbers.
[Phys. Rev. Fluids 4, 052601(R)] Published Wed May 01, 2019
Author(s): Martin Magill, Aaron Coutino, Benjamin A. Storer, Marek Stastna, and Francis J. Poulin
Vortices in a model of the solar tachocline decay into pairs of stable donutlike Alfvén waves. These propagate zonally in opposite directions, colliding periodically. Nonlinear effects distort the waves significantly after each collision, but between collisions their shapes and speed remain fixed.
[Phys. Rev. Fluids 4, 053701] Published Wed May 01, 2019
Author(s): Jie Zhang, Long Chen, and Ming-Jiu Ni
Numerical studies show that different interactions between a pair of bubbles rising side by side are greatly dependent on the development of the wake vortices behind the bubbles. The bubble size, the separated distance, and the fluid properties all affect the formation of the wake patterns.
[Phys. Rev. Fluids 4, 043604] Published Tue Apr 30, 2019
Author(s): Metin Hatipogullari, Christophe Wylock, Marc Pradas, Serafim Kalliadasis, and Pierre Colinet
Using a simple configuration, we study stick-slip and hysteresis mostly analytically, and compare our results to the classical theories. In particular, we highlight the changes which occur when varying the size of the system relative to the typical size of the heterogeneity.
[Phys. Rev. Fluids 4, 044008] Published Tue Apr 30, 2019
Author(s): Alvaro Marin, Stefan Karpitschka, Diego Noguera-Marín, Miguel A. Cabrerizo-Vílchez, Massimiliano Rossi, Christian J. Kähler, and Miguel A. Rodríguez Valverde
Coffee-ring stains occur via the classical capillary flows. However, when salt is present in the solution, experiments and numerical simulations reveal that ring-shaped stains can also occur due to solutal Marangoni flows instead.
[Phys. Rev. Fluids 4, 041601(R)] Published Mon Apr 29, 2019
Author(s): Ehsan Esmaili, Pranav Shukla, Joseph D. Eifert, and Sunghwan Jung
An investigation into the dynamics of bubble-wall interaction—to assess its potential to remove bacteria on surfaces—finds that the shear stress generated by an impacting bubble is more than the bacterium adhesion force.
[Phys. Rev. Fluids 4, 043603] Published Mon Apr 29, 2019
Author(s): Paul Götzfried, Mohammad S. Emran, Emmanuel Villermaux, and Jörg Schumacher
High-Schmidt-number turbulent mixing of a freely decaying passive scalar is compared in the Eulerian and Lagrangian frames of reference. Also, the passive scalar statistics is connected to that of the local flow compression rates, which is collected along the Lagrangian particle trajectories.
[Phys. Rev. Fluids 4, 044607] Published Mon Apr 29, 2019
Author(s): C. Barbosa, D. Legendre, and R. Zenit
A study of bubbles sliding over a wall shows that the shape changes depending on the angle. The shape is affected by gravity for small angles and inertia for large ones.
[Phys. Rev. Fluids 4, 043602] Published Fri Apr 26, 2019
Author(s): J. J. J. Gillissen and H. J. Wilson
The laminar flow in the gap between a rotating inner cylinder and a stationary outer cylinder is destabilized by adding particles. A theoretical study relates this effect to the anisotropic microstructure of the suspension.
[Phys. Rev. Fluids 4, 043301] Published Thu Apr 25, 2019
Author(s): Antonia Statt, Michael P. Howard, and Athanassios Z. Panagiotopoulos
Surprising secondary flows develop in reverse nonequilibrium simulations when the simulation box is elongated in the direction of flow.
[Phys. Rev. Fluids 4, 043905] Published Thu Apr 25, 2019
Author(s): Olamide Oladosu, Aqib Hasnain, Paris Brown, Ian Frigaard, and Kamran Alba
Displacement of a water-based solution by an oil-based one is studied experimentally. Applications are found in cleaning-in-place processes present in the petroleum and food processing industries. An interesting wall pinning effect due to wetting/nonwetting properties of solutions is observed.
[Phys. Rev. Fluids 4, 044007] Published Wed Apr 24, 2019
Author(s): Dang Minh Nguyen, Muttikulangara Swaminathan Sanathanan, Jianmin Miao, David Fernandez Rivas, and Claus-Dieter Ohl
Two bubbles communicate with each other acoustically without being affected by any external sound field. We have performed an experiment showing that at the right distance, their connection becomes strong enough that they synchronize perfectly and eventually merge as one.
[Phys. Rev. Fluids 4, 043601] Published Mon Apr 22, 2019
Author(s): Benjamin C. Martell, Jeffrey Tithof, and Douglas H. Kelley
Particles at the top and bottom of a thin fluid layer are simultaneously tracked to measure how well such experiments model two-dimensional flow. Top and bottom flow directions align well. The bottom-to-top speed ratio nearly matches laminar predictions, even for chaotic flow, except in misaligned regions.
[Phys. Rev. Fluids 4, 043904] Published Mon Apr 22, 2019
Dynamics of potential vorticity staircase evolution and step mergers in a reduced model of beta-plane turbulence
Author(s): M. A. Malkov and P. H. Diamond
Quasigeostrophic turbulence can self-organize into “staircases”—periodic arrays of turbulence separated by layers of potential vorticity (PV) gradients. These patterns are recovered from a reduced model that couples mean PV and potential enstrophy. Sharpening occurs due to bistable mixing of mean PV.
[Phys. Rev. Fluids 4, 044503] Published Mon Apr 22, 2019