Latest papers in fluid mechanics

Dynamics of a thin film driven by a moving pressure source

Physical Review Fluids - Tue, 11/06/2018 - 10:00

Author(s): D. Lunz and P. D. Howell

Motivated by plasma particles impacting a liquid-metal divertor, an analysis is performed to investigate how a liquid’s free surface is deflected by a moving applied pressure. It is found that the plasma can be swept up and down the liquid in order to spread the heat load, however, this may induce dangerously large deflections.

[Phys. Rev. Fluids 3, 114801] Published Tue Nov 06, 2018

Counterion flow through a deformable and charged nanochannel

Physical Review E - Thu, 11/01/2018 - 10:00

Author(s): Mpumelelo Matse, Peter Berg, and Michael Eikerling

A theoretical model is developed that describes nonlinear coupling between wall deformation and water and ion flows in a charged, deformable nanochannel whose viscoelasticity is governed by the Kelvin-Voigt model. Using continuum mean-field theories for mass and momentum conservation of the solid-li...

[Phys. Rev. E 98, 053101] Published Thu Nov 01, 2018

Particle collection by permeable drops

Physical Review Fluids - Thu, 11/01/2018 - 10:00

Author(s): Robert H. Davis and Alexander Z. Zinchenko

Hydrophobic particles are selectively separated from aqueous suspension by a novel oil-in-water binder. The collection efficiency is predicted in this work by a hydrodynamic trajectory analysis, and shown to be greatly enhanced by water permeation through the oil layer.

[Phys. Rev. Fluids 3, 113601] Published Thu Nov 01, 2018

Three-dimensional instabilities and negative eddy viscosity in thin-layer flows

Physical Review Fluids - Thu, 11/01/2018 - 10:00

Author(s): Alexandros Alexakis

An investigation of how large-scale flow is affected by changes in the properties of small-scale flows, the layer thickness, and viscosity is presented.

[Phys. Rev. Fluids 3, 114601] Published Thu Nov 01, 2018

Local origin of mode-B secondary instability in the flow past a circular cylinder

Physical Review Fluids - Wed, 10/31/2018 - 10:00

Author(s): Yogesh Jethani, Kamal Kumar, A. Sameen, and Manikandan Mathur

Local stability equations are solved along closed fluid particle trajectories in the cylinder wake for Reynolds numbers in the range of 50 to 300. A bifurcation is shown to occur at Re≈250 and is argued to be related to the emergence of the well-known mode-B secondary instability.

[Phys. Rev. Fluids 3, 103902] Published Wed Oct 31, 2018

Mesoscopic model for soft flowing systems with tunable viscosity ratio

Physical Review Fluids - Wed, 10/31/2018 - 10:00

Author(s): Linlin Fei, Andrea Scagliarini, Andrea Montessori, Marco Lauricella, Sauro Succi, and Kai H. Luo

We further develop a two-range pseudopotential Lattice Boltzmann method for soft flowing systems using tunable surface tension and viscosity ratio. It is applicable to multicomponent fluids with a viscosity-independent disjoining pressure, a key to the microfluidic design of new porous materials.

[Phys. Rev. Fluids 3, 104304] Published Wed Oct 31, 2018

Law of the wall for small-scale streamwise turbulence intensity in high-Reynolds-number turbulent boundary layers

Physical Review Fluids - Wed, 10/31/2018 - 10:00

Author(s): B. Ganapathisubramani

Following the dimensional analysis approach of previous works, a law-of-the-wall is proposed for small-scale fluctuations in turbulent wall-flow. Experimental data shows that this universal scaling law extends across almost the entire wall-layer and exhibits a logarithmic trend in the outer region.

[Phys. Rev. Fluids 3, 104607] Published Wed Oct 31, 2018

Deformation of a flexible fiber settling in a quiescent viscous fluid

Physical Review Fluids - Tue, 10/30/2018 - 10:00

Author(s): Benjamin Marchetti, Veronica Raspa, Anke Lindner, Olivia du Roure, Laurence Bergougnoux, Élisabeth Guazzelli, and Camille Duprat

A flexible fiber settling in a viscous fluid deforms and reorients to adopt eventually a more or less pronounced “U” shape, regardless of its initial configuration. Three different regimes depending on the relative magnitude of gravitational and elastic forces are identified.

[Phys. Rev. Fluids 3, 104102] Published Tue Oct 30, 2018

Slip-flow lattice-Boltzmann simulations in ducts and porous media: A full rehabilitation of spurious velocities

Physical Review E - Mon, 10/29/2018 - 10:00

Author(s): M. Aminpour, S. A. Galindo-Torres, A. Scheuermann, and L. Li

Slip flow in ducts and porous media is simulated using lattice-Boltzmann method incorporated with interfacial force models. The dependence of the results on the viscosity, LBM scheme (D3Q15 and D3Q19) and the relaxation time model (single- or multirelaxation time) is investigated. The severity of sp...

[Phys. Rev. E 98, 043110] Published Mon Oct 29, 2018

Vesicle dynamics in confined steady and harmonically modulated Poiseuille flows

Physical Review E - Mon, 10/29/2018 - 10:00

Author(s): Zakaria Boujja, Chaouqi Misbah, Hamid Ez-Zahraouy, Abdelilah Benyoussef, Thomas John, Christian Wagner, and Martin Michael Müller

We present a numerical study of the time-dependent motion of a two-dimensional vesicle in a channel under an imposed flow. In a Poiseuille flow the shape of the vesicle depends on the flow strength, the mechanical properties of the membrane, and the width of the channel as reported in the past. This...

[Phys. Rev. E 98, 043111] Published Mon Oct 29, 2018

Shape evolution and bubble formation of acoustically levitated drops

Physical Review Fluids - Mon, 10/29/2018 - 10:00

Author(s): Wenli Di, Zehui Zhang, Lin Li, Kejun Lin, Jun Li, Xiaoguang Li, Bernard P. Binks, Xiaopeng Chen, and Duyang Zang

Experiments shows that with increasing sound intensity, an acoustically levitated drop buckles into a bowl shape and experiences a drastic expansion and closure, leading to the formation of an air bubble. This is attributed to the enhanced suction effect at the film rim due to the occurrence of resonance with sound field.

[Phys. Rev. Fluids 3, 103606] Published Mon Oct 29, 2018

Entry of a sphere into a water-surfactant mixture and the effect of a bubble layer

Physical Review Fluids - Mon, 10/29/2018 - 10:00

Author(s): N. B. Speirs, M. M. Mansoor, R. C. Hurd, S. I. Sharker, W. G. Robinson, B. J. Williams, and T. T. Truscott

An experimental study shows that splash formation is not reduced when spheres fall into water with a layer of soap bubbles on top. Instead, the bubble layer causes entrained air cavities to form at lower impact velocities. Results also show that the surfactant causes cavity formation to become radius dependent in cases where there is no bubble layer.

[Phys. Rev. Fluids 3, 104004] Published Mon Oct 29, 2018

In-plane elasticity controls the full dynamics of red blood cells in shear flow

Physical Review Fluids - Thu, 10/25/2018 - 11:00

Author(s): Simon Mendez and Manouk Abkarian

Red blood cells are modeled by an axisymmetric ellipsoid of fixed shape with internal circulation in shear flow without inertia. When accounting for membrane in-plane elasticity the model predicts the expected behaviors of flipping with orbit selection, rolling, frisbeeing, kayaking, and swinging.

[Phys. Rev. Fluids 3, 101101(R)] Published Thu Oct 25, 2018

Numerical simulations of a rising drop with shape oscillations in the presence of surfactants

Physical Review Fluids - Thu, 10/25/2018 - 11:00

Author(s): Antoine Piedfert, Benjamin Lalanne, Olivier Masbernat, and Frédéric Risso

Shape-oscillating droplets rising in a liquid are simulated with insoluble surfactants adsorbed at their interface. Conditions are reported in which the average surface tension gradient induces a significant decrease of the rise velocity but does not impact the oscillation dynamics.

[Phys. Rev. Fluids 3, 103605] Published Thu Oct 25, 2018

Large-eddy simulations of turbulent thermal convection using renormalized viscosity and thermal diffusivity

Physical Review E - Wed, 10/24/2018 - 11:00

Author(s): Sumit Vashishtha, Mahendra K. Verma, and Roshan Samuel

In this paper we employ renormalized viscosity and thermal diffusivity to construct a subgrid-scale model for large eddy simulation (LES) of turbulent thermal convection. For LES, we add νren∝Πu1/3(π/Δ)−4/3 to the kinematic viscosity; here Πu is the turbulent kinetic energy flux, and Δ is the grid s...

[Phys. Rev. E 98, 043109] Published Wed Oct 24, 2018

Electrodeformation of vesicles suspended in a liquid medium

Physical Review Fluids - Wed, 10/24/2018 - 11:00

Author(s): Adnan Morshed, Prashanta Dutta, Mohammad Robiul Hossan, and Robert Dillon

The electrodeformation of a bio-vesicle suspended in liquid media depends on the conductivity ratio of fluid and vesicle, applied electric field, membrane capacitive charging, and vesicle initial shape. Our theoretical study provides important insights on this complex fluid-structure interaction.

[Phys. Rev. Fluids 3, 103702] Published Wed Oct 24, 2018

Force on a compressible sphere and the resonance of a bubble in standing surface acoustic waves

Physical Review E - Tue, 10/23/2018 - 11:00

Author(s): Shen Liang, Wang Chaohui, and Hu Qiao

In this paper, the theory for acoustic radiation force exerted by standing surface acoustic waves (SSAWs) is extended to a compressible sphere in inviscid fluids. The conventional theory, developed in plane standing waves, fails to predict the radiation force incident on particles in the SSAW. Our e...

[Phys. Rev. E 98, 043108] Published Tue Oct 23, 2018

Stokes' second problem and reduction of inertia in active fluids

Physical Review Fluids - Mon, 10/22/2018 - 11:00

Author(s): Jonasz Słomka, Alex Townsend, and Jörn Dunkel

Simulations predict that a pendulum immersed in an active fluid oscillates faster than in a passive fluid due to a reduction of the fluid inertia. The decrease in inertia is mediated by topological defects in the stress field, which can effectively decouple the bulk flow dynamics from the pendulum.

[Phys. Rev. Fluids 3, 103304] Published Mon Oct 22, 2018

Beyond the coffee-ring effect: Pattern formation by wetting and spreading of drops

Physical Review E - Fri, 10/19/2018 - 11:00

Author(s): Dileep Mampallil, Meenakshi Sharma, Ashwini Sen, and Shubham Sinha

Drying of colloidal drops on solid surfaces is the widely known method to form self-assembled patterns. The underlying principle of this method is the phenomenon known as the coffee-ring effect. Here, we report a phenomenon of pattern formation involving not drying but conversely wetting and spreadi...

[Phys. Rev. E 98, 043107] Published Fri Oct 19, 2018

Jump-to-contact instability: The nanoscale mechanism of droplet coalescence in air

Physical Review Fluids - Fri, 10/19/2018 - 11:00

Author(s): Véronique Chireux, Matthieu Protat, Frédéric Risso, Thierry Ondarçuhu, and Philippe Tordjeman

Atomic Force Microscope observations find that two drops of radii 0.7 to 70 micrometers jump to contact when separated by a distance that scales as (HReq/γ)1/3 for small drops and as (H/γ)1/2 for larger drops.

[Phys. Rev. Fluids 3, 102001(R)] Published Fri Oct 19, 2018


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