Physical Review Fluids
Author(s): Xingjian Lin, Jie Wu, Tongwei Zhang, and Liming Yang
The collective locomotion of two tandem autopropelled flapping foils is greatly affected by the phase difference. Two distinct vortex interactions are observed—merging interaction and broken interaction—which respectively result in the highest efficiency for the follower and the leader.
[Phys. Rev. Fluids 4, 054101] Published Fri May 17, 2019
Predicting the maximum spreading of a liquid drop impacting on a solid surface: Effect of surface tension and entrapped air layer
Author(s): Thijs C. de Goede, Karla G. de Bruin, Noushine Shahidzadeh, and Daniel Bonn
At low impact velocities, a droplet does not immediately make contact with a surface because of an entrapped air layer, leading to delayed surface wetting. High-speed images are used to investigate the influence of this entrapped air layer and the surface wettability on droplet spreading.
[Phys. Rev. Fluids 4, 053602] Published Wed May 15, 2019
Author(s): Nicholas C. White and Sandra M. Troian
Lyapunov and non-modal stability analysis reveal why stationary and self-similar capillary flows in slender open triangular channels are so stable to disturbances. This robust feature allows superior flow management for applications ranging from space micropropulsion to microfluidic diagnostics.
[Phys. Rev. Fluids 4, 054003] Published Wed May 15, 2019
Author(s): Yuhan Huang, Zhenhua Xia, Minping Wan, Yipeng Shi, and Shiyi Chen
In direct numerical simulations of spanwise rotating plane Couette flow, hysteresis is found between a 2-pair-roll-cell as the rotation increases to a 3-pair-roll-cell when the rotation decreases.
[Phys. Rev. Fluids 4, 052401(R)] Published Tue May 14, 2019
Characterization of blood velocity in arteries using a combined analytical and Doppler imaging approach
Author(s): Bchara Sidnawi, Zhen Chen, Chandra Sehgal, Sridhar Santhanam, and Qianhong Wu
Using ultrasound Doppler imaging we experimentally and analytically reconstruct the blood flow field in arteries and provide an in−vivo-validated, noninvasive, and reliable Wall Shear Stress (WSS) estimation. WSS is a major mechanical modulator of many functions of the cardiovascular system.
[Phys. Rev. Fluids 4, 053101] Published Mon May 13, 2019
Author(s): Jiaao Hao and Chih-Yung Wen
An accurate and efficient model based on the maximum entropy principle is established for the vibrational excitation and dissociation of oxygen. Good agreement with state-specific calculations and recent experimental data is obtained.
[Phys. Rev. Fluids 4, 053401] Published Mon May 13, 2019
Author(s): Charlotte de Blois, Mathilde Reyssat, Sébastien Michelin, and Olivier Dauchot
Experimental measurements of the velocity field around a droplet swimming close to a wall demonstrate the critical impact of confinement.
[Phys. Rev. Fluids 4, 054001] Published Mon May 13, 2019
Author(s): Kévin Patouillet, Laurent Davoust, Olivier Doche, and Jules Delacroix
Channel viscosimetry makes it possible to estimate surface viscosity of a layer of surfactants or metal oxides. A new model is presented with surface curvature effects accounted for, regardless of whether or not the supporting liquid is wetting or if the contaminated surface is Newtonian.
[Phys. Rev. Fluids 4, 054002] Published Mon May 13, 2019
Author(s): Jean-Régis Angilella
When approaching a recirculation cell, Brownian aerosols can enter the cell or slip along its border or drift away. Determining which particles do what is very challenging. A general analytical expression for the probability of capture of aerosols in such cells is derived.
[Phys. Rev. Fluids 4, 054304] Published Mon May 13, 2019
Author(s): Igor V. Naumov, Vladimir G. Glavny, Bulat R. Sharifullin, and Vladimir N. Shtern
An experimental study reveals the formation of a thin circulation layer (TCL) adjacent to the entire interface of a two-fluid swirling flow in a sealed, vertical cylindrical container. The TCL scenario differs from that predicted numerically.
[Phys. Rev. Fluids 4, 054702] Published Mon May 13, 2019
Author(s): Wenhu Han, Cheng Wang, and Chung K. Law
A numerical simulation finds that a three-dimensional conical oblique wave takes on a cellular structure on the front, presenting a fish-scale shape. The cell shape becomes relatively irregular as the heat release is increased.
[Phys. Rev. Fluids 4, 053201] Published Fri May 10, 2019
Author(s): Alban Sauret, Adrien Gans, Bénédicte Colnet, Guillaume Saingier, Martin Z. Bazant, and Emilie Dressaire
We develop a passive method of soft filtration which leverages interfacial forces to prevent the contamination of substrates withdrawn from a liquid polluted by microparticles and micro-organisms.
[Phys. Rev. Fluids 4, 054303] Published Fri May 10, 2019
Author(s): L. Zhao, K. Gustavsson, R. Ni, S. Kramel, G. A. Voth, H. I. Andersson, and B. Mehlig
With experiments and direct numerical simulations we study the angular distribution of symmetry axes of nearby small spheroids in a turbulent flow when inertial effects are negligible. We find the angles to be unexpectedly large with a fractal attractor and a distribution with power law tails.
[Phys. Rev. Fluids 4, 054602] Published Fri May 10, 2019
Author(s): P. A. Srinivasan, L. Guastoni, H. Azizpour, P. Schlatter, and R. Vinuesa
The long short-term memory (LSTM) neural network is used to predict the temporal evolution of a low-order representation of near-wall turbulence. This network leads to excellent predictions of turbulence statistics and of the system dynamics, characterized by Poincaré maps and Lyapunov exponents.
[Phys. Rev. Fluids 4, 054603] Published Fri May 10, 2019
Author(s): Binbin Wang and Scott A. Socolofsky
Mean flow and turbulence in bubble-in-chain induced flows are experimentally observed at various release frequencies and flow rates. We find that horizontal water velocity profiles collapse to a universal Gaussian distribution and one-dimensional velocity spectra to a consistent slope of −3.
[Phys. Rev. Fluids 4, 054302] Published Thu May 09, 2019
Author(s): Tiantian Zhang, James Schloss, Andreas Thomasen, Lee James O'Riordan, Thomas Busch, and Angela White
A study of vortex dynamics in a confined superfluid shows that a system of three co-rotating quantum vortices and one vortex of opposite rotation exhibit chaotic dynamics. We find the onset of chaos is seeded through the close approach and separation of vortices in a scattering event.
[Phys. Rev. Fluids 4, 054701] Published Thu May 09, 2019
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