Physical Review Fluids

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Updated: 23 hours 14 min ago

Universal molecular-kinetic scaling relation for slip of a simple fluid at a solid boundary

Wed, 06/26/2019 - 11:00

Author(s): Gerald J. Wang and Nicolas G. Hadjiconstantinou

A molecular-kinetic model, based on thermally activated processes, is developed for the slip of a simple fluid on a smooth solid boundary. Navier slip is recovered at low shear-rates. Predictions at higher shear-rates are tested against experiments and MD simulations.

[Phys. Rev. Fluids 4, 064201] Published Wed Jun 26, 2019

Propulsion driven by self-oscillation via an electrohydrodynamic instability

Mon, 06/24/2019 - 11:00

Author(s): Lailai Zhu and Howard A. Stone

When a flexible elastic filament is attached to a Quincke rotating sphere, an elasto-electro-hydrodynamic instability leads to self-propulsion of the composite system.

[Phys. Rev. Fluids 4, 061701(R)] Published Mon Jun 24, 2019

Dynamics of gravity-driven viscoelastic films on wavy walls

Mon, 06/24/2019 - 11:00

Author(s): Arjun Sharma, Prasun K. Ray, and Demetrios T. Papageorgiou

An investigation finds that instability in gravity-driven thin viscoelastic films can be substantively enhanced or suppressed by sinusoidal wall topography with an appropriately chosen wavelength. Topography also introduces finer temporal scales in the film dynamics, and simulations produce a broad range of nonlinear states.

[Phys. Rev. Fluids 4, 063305] Published Mon Jun 24, 2019

Electroosmotic flow in soft microchannels at high grafting densities

Mon, 06/24/2019 - 11:00

Author(s): Arman Sadeghi, Milad Azari, and Steffen Hardt

The ion partitioning effect due to polyelectrolyte layer (PEL)-electrolyte permittivity contrast in soft microchannels leads to depletion of electrolyte ions within the PEL. This effect, surprisingly, magnifies the electroosmotic flow rate because of the space charge increase outside the PEL.

[Phys. Rev. Fluids 4, 063701] Published Mon Jun 24, 2019

Effect of elastic walls on suspension flow

Fri, 06/21/2019 - 11:00

Author(s): Marco Edoardo Rosti, Mehdi Niazi Ardekani, and Luca Brandt

A suspension of rigid particles in plane Couette flow with elastic boundaries is simulated numerically. Reduction in apparent viscosity for the more deformable boundaries is modeled as a concentration reduction as the volume for particles expands in amount equal to the boundary elastic deformation.

[Phys. Rev. Fluids 4, 062301(R)] Published Fri Jun 21, 2019

Dynamic jamming of dense suspensions under tilted impact

Fri, 06/21/2019 - 11:00

Author(s): Endao Han, Liang Zhao, Nigel Van Ha, S. Tonia Hsieh, Daniel B. Szyld, and Heinrich M. Jaeger

High-speed ultrasound imaging is used to reconstruct the three-dimensional flow field of dense cornstarch suspensions under tilted impact. Experiments show how jamming fronts propagate and get deformed in a nonaxisymmetric manner under different impact angles.

[Phys. Rev. Fluids 4, 063304] Published Fri Jun 21, 2019

Group theory analysis of early-time scale-dependent dynamics of the Rayleigh-Taylor instability with time varying acceleration

Fri, 06/21/2019 - 11:00

Author(s): Desmond L. Hill, Aklant K. Bhowmick, Dan V. Ilyin, and Snezhana I. Abarzhi

Group theory analysis of the Rayleigh-Taylor instability with an acceleration varying in time finds that the early time behavior depends on whether the acceleration decays faster or slower than 1/t2.

[Phys. Rev. Fluids 4, 063905] Published Fri Jun 21, 2019

Resonant response and optimal energy harvesting of an elastically mounted pitching and heaving hydrofoil

Thu, 06/20/2019 - 11:00

Author(s): Yunxing Su and Kenneth Breuer

Experiments using a cyber-physical hydrofoil, tested over a wide range of stiffness and damping coefficients, reveal that the optimal response is achieved at the structural resonant frequency where the leading-edge vortex formation is synchronized with the foil pithing and heaving.

[Phys. Rev. Fluids 4, 064701] Published Thu Jun 20, 2019

Rotational dynamics of a particle in a turbulent stream

Wed, 06/19/2019 - 11:00

Author(s): Yayun Wang, Adam Sierakowski, and Andrea Prosperetti

Numerical simulations of turbulent flow past a sphere immersed in decaying turbulence, free to rotate around a fixed center, are presented. This arrangement allows the same simulations with and without the sphere, thus permitting the identification of the flow features that most affect the sphere rotation.

[Phys. Rev. Fluids 4, 064304] Published Wed Jun 19, 2019

Particle size selection in capillary instability of locally heated coaxial fiber

Tue, 06/18/2019 - 11:00

Author(s): Saviz Mowlavi, Isha Shukla, P.-T. Brun, and François Gallaire

An analysis of the drop-size selection mechanism in a locally heated silicon-in-silica coaxial fiber is presented. Surprisingly, it is found that the size of the silicon drops is independent of the linear stability properties of the system and is instead set by nonlinear effects.

[Phys. Rev. Fluids 4, 064003] Published Tue Jun 18, 2019

Role of the near-tip region of a fin in fish propulsion

Mon, 06/17/2019 - 11:00

Author(s): F. J. Huera-Huarte and Morteza Gharib

We examine the effects of locally altering the tip region of a periodic flapping fin system with a low order robotic model and load, motion, and wake measurements. This actuation modifies propulsive performance and unveils the importance of the phase difference between the fin and the tip.

[Phys. Rev. Fluids 4, 063103] Published Mon Jun 17, 2019

Bypass transition delay using oscillations of spanwise wall velocity

Mon, 06/17/2019 - 11:00

Author(s): Prabal S. Negi, Maneesh Mishra, Philipp Schlatter, and Martin Skote

Bypass transition in boundary layers is governed by streak instability. An investigation of the effect of oscillatory wall-control on bypass transition shows that transition delay is due to streak attenuation via the modification of the eigenfunction of the Orr-Sommerfeld operator.

[Phys. Rev. Fluids 4, 063904] Published Mon Jun 17, 2019

Topological mixing of yield stress materials

Fri, 06/14/2019 - 11:00

Author(s): D. R. Lester and A. Chryss

Chaotic mixing of yield stress fluids is considered in a novel static mixer that imparts uniformly efficient mixing due to the underlying topology of the device. Experimental and computational studies indicate that mixing is largely insensitive to flow dynamics, boundary conditions, and fluid rheology.

[Phys. Rev. Fluids 4, 064502] Published Fri Jun 14, 2019

Small-scale flow topologies in decaying isotropic turbulence laden with finite-size droplets

Thu, 06/13/2019 - 11:00

Author(s): Michael S. Dodd and Lluís Jofre

The small-scale flow topologies in droplet-resolved direct numerical simulations of isotropic turbulence are classified using tensor invariants. The results show that when approaching the droplet surface, the flow topologies fundamentally change from those found in isotropic turbulence to boundary-layer-like structures.

[Phys. Rev. Fluids 4, 064303] Published Thu Jun 13, 2019

Frozen waves in turbulent mixing layers

Thu, 06/13/2019 - 11:00

Author(s): Benoît-Joseph Gréa and Antoine Briard

The horizontal vibrations of an interface between miscible fluids trigger a parametric instability, leading to frozen wave patterns. Theory and numerical simulations reveal that the mixing layer size varies as the square of the forcing amplitude in the turbulent regime.

[Phys. Rev. Fluids 4, 064608] Published Thu Jun 13, 2019

Strong turbulence for vibrating plates: Emergence of a Kolmogorov spectrum

Thu, 06/13/2019 - 11:00

Author(s): Gustavo Düring, Christophe Josserand, Giorgio Krstulovic, and Sergio Rica

In the low viscosity liquid and zero thickness vibrating elastic sheet, turbulent behavior is observed. We find the same Kolmogorov spectrum cascade for energy redistribution per scale Ek∼P2/3k−5/3 in both, apparently, completely disparate physical situations.

[Phys. Rev. Fluids 4, 064804] Published Thu Jun 13, 2019

Vectorial structure of the near-wall premixed flame

Wed, 06/12/2019 - 11:00

Author(s): Peipei Zhao, Lipo Wang, and Nilanjan Chakraborty

A turbulent premixed flame anchored by a solid wall can reach a statistically stationary state. Overall the configuration is counterflowlike. Flame-wall interactions under such conditions are key to understanding combustion in a confined space and in developing wall flame models. A numerical study is presented.

[Phys. Rev. Fluids 4, 063203] Published Wed Jun 12, 2019

Turning strategies for plunging elastic plate propulsor

Wed, 06/12/2019 - 11:00

Author(s): Peter D. Yeh, Ersan Demirer, and Alexander Alexeev

Complex actuation of a caudal fin can generate turning moments enabling underwater swimmer navigation. A numerical study explores the hydrodynamics resulting from two actuation strategies leading to pitching and yaw moments.

[Phys. Rev. Fluids 4, 064101] Published Wed Jun 12, 2019

Inertial effects on the dynamics of rigid heavy fibers in isotropic turbulence

Wed, 06/12/2019 - 11:00

Author(s): Sofia Kuperman, Lilach Sabban, and René van Hout

Holographic cinematography is used to measure rotational and translational dynamics of inertial fibers in isotropic turbulence. Results show that for the present parameter range, translational motion is similar to that for spheres. In contrast, tumbling rates peaked at an intermediate Stokes number.

[Phys. Rev. Fluids 4, 064301] Published Wed Jun 12, 2019

Quantitative study of the rheology of frictional suspensions: Influence of friction coefficient in a large range of viscous numbers

Wed, 06/12/2019 - 11:00

Author(s): William Chèvremont, Bruno Chareyre, and Hugues Bodiguel

A numerical study of sheared suspensions of frictional and frictionless rigid spheres finds that macroscopic friction in granular suspensions is nearly independent of interparticle contact friction, and besides contact lubrication, the viscous contribution of the pore fluid is negligibly small.

[Phys. Rev. Fluids 4, 064302] Published Wed Jun 12, 2019