Physical Review Fluids

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Lean premixed reacting flows with swirl and wall-separation zones in a contracting open circular chamber

Tue, 11/06/2018 - 10:00

Author(s): Zvi Rusak, Yuxin Zhang, Jung J. Choi, and Shixiao Wang

A model problem of low-Mach number lean premixed reacting swirling flows with wall-separation zones in a contracting open chamber is studied. A theoretical feasibility for a technology of swirl-assisted combustion where the reaction zone is supported by a wall-separation zone is established.

[Phys. Rev. Fluids 3, 113201] Published Tue Nov 06, 2018

Influence of interfacial elasticity on liquid entrainment in thin foam films

Tue, 11/06/2018 - 10:00

Author(s): Gigi Lin, John M. Frostad, and Gerald G. Fuller

Thin-film experiments with an interferometric apparatus show an absence of a strong relationship between interfacial elasticity and liquid entrainment in thin foam films, which can affect rational design of aesthetic and tactile properties in foaming consumer products.

[Phys. Rev. Fluids 3, 114001] Published Tue Nov 06, 2018

Temperature gradient induced double stabilization of the evaporation front within a drying porous medium

Tue, 11/06/2018 - 10:00

Author(s): N. Vorhauer, E. Tsotsas, and M. Prat

The flow of water vapor against temperature gradients naturally occurring in drying of porous media leads to condensation and simultaneous gas-liquid invasion of pore space. This phenomenon is studied with a model porous medium in a microfluidic device and a pore network model of drying and imbibition.

[Phys. Rev. Fluids 3, 114201] Published Tue Nov 06, 2018

Dynamics of a thin film driven by a moving pressure source

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

Particle collection by permeable drops

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

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

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

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

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

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

Shape evolution and bubble formation of acoustically levitated drops

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

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

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

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

Electrodeformation of vesicles suspended in a liquid medium

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

Stokes' second problem and reduction of inertia in active 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

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

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

Electrokinetics of a particle attached to a fluid interface: Electrophoretic mobility and interfacial deformation

Fri, 10/19/2018 - 11:00

Author(s): Michael Eigenbrod, Florian Bihler, and Steffen Hardt

The electrophoretic mobility of a particle at the interface between two fluids is computed. For thin Debye layers, the Smoluchowki mobility is recovered. Generally, the mobility depends on the contact angle between the fluids and the particle. The interfacial deformation is also calculated.

[Phys. Rev. Fluids 3, 103701] Published Fri Oct 19, 2018

Plastron morphology and drag of a superhydrophobic surface in turbulent regime

Thu, 10/18/2018 - 11:00

Author(s): D. Reholon and S. Ghaemi

We perform drag force and particle tracking velocimetry measurements on a body-of-revolution coated with a superhydrophobic layer for Re between 5×105 and 1.5×106. As Re increases, drag reduction decreases, and a full plastron becomes isolated air bubbles as thin menisci.

[Phys. Rev. Fluids 3, 104003] Published Thu Oct 18, 2018

Helicity in superfluids: Existence and the classical limit

Thu, 10/18/2018 - 11:00

Author(s): Hridesh Kedia, Dustin Kleckner, Martin W. Scheeler, and William T. M. Irvine

The analog of hydrodynamic helicity in superfluids is zero for all flows. A semiclassical limit is found in the link and writhe of bundles of superfluid vortices. Numerical simulations show that the dynamics of semiclassical helicity closely resemble those seen in experiments in viscous fluids.

[Phys. Rev. Fluids 3, 104702] Published Thu Oct 18, 2018