Physical Review Fluids

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Updated: 23 hours 28 min ago

Phase difference effect on collective locomotion of two tandem autopropelled flapping foils

Fri, 05/17/2019 - 11:00

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

Wed, 05/15/2019 - 11:00

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

Why capillary flows in slender triangular grooves are so stable against disturbances

Wed, 05/15/2019 - 11:00

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

Hysteresis behavior in spanwise rotating plane Couette flow with varying rotation rates

Tue, 05/14/2019 - 11:00

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

Mon, 05/13/2019 - 11:00

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

Maximum entropy modeling of oxygen vibrational excitation and dissociation

Mon, 05/13/2019 - 11:00

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

Flow field around a confined active droplet

Mon, 05/13/2019 - 11:00

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

Mannheimer and Schechter model revisited: Viscosimetry of a (non-)Newtonian and curved interface

Mon, 05/13/2019 - 11:00

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

Probability of noise-induced separatrix crossing for inertial particles in flows

Mon, 05/13/2019 - 11:00

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

Formation of a thin circulation layer in a two-fluid rotating flow

Mon, 05/13/2019 - 11:00

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

Three-dimensional simulation of oblique detonation waves attached to cone

Fri, 05/10/2019 - 11:00

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

Capillary filtering of particles during dip coating

Fri, 05/10/2019 - 11:00

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

Passive directors in turbulence

Fri, 05/10/2019 - 11:00

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

Predictions of turbulent shear flows using deep neural networks

Fri, 05/10/2019 - 11:00

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

Characteristics of mean flow and turbulence in bubble-in-chain induced flows

Thu, 05/09/2019 - 11:00

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

Chaotic few-body vortex dynamics in rotating Bose-Einstein condensates

Thu, 05/09/2019 - 11:00

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

Drop impact close to the edge of an inclined substrate: Liquid sheet formation and breakup

Wed, 05/08/2019 - 11:00

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

Deformation and stability of a viscous electrolyte drop in a uniform electric field

Wed, 05/08/2019 - 11:00

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

Influence of Reynolds number on the motion of settling, bidisperse inertial particles in turbulence

Wed, 05/08/2019 - 11:00

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

Tue, 05/07/2019 - 11:00

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