Physical Review Fluids
Author(s): Joshua A. Dijksman, Shomeek Mukhopadhyay, Robert P. Behringer, and Thomas P. Witelski
Temperature gradients affect fluid interfaces by changing the local surface tension. Both experiments and numerics show that in rotating thin liquid films, these Marangoni stresses significantly affect fluid film height profile dynamics and equilibria.
[Phys. Rev. Fluids 4, 084103] Published Mon Aug 19, 2019
Author(s): H. Chen, M. Marengo, and A. Amirfazli
An experimental study finds that when a drop impacts close to the edge of a surface, part of the lamella spreads out of the surface. Depending on the normalized distance to the edge, the free lamella can either recede back onto the surface, or completely break off at the surface edge.
[Phys. Rev. Fluids 4, 083601] Published Fri Aug 16, 2019
Author(s): San To Chan, Jesse T. Ault, Simon J. Haward, E. Meiburg, and Amy Q. Shen
Experiments and simulations are combined to study flows in a T-mixer with offset inlets, whose stability is coupled to the vortex breakdown structure in the system. This leads to an unexpected flow regime in which increasing the flow rate can re-stabilize steady-state solutions of the flow.
[Phys. Rev. Fluids 4, 084701] Published Thu Aug 15, 2019
Signature of electroconvective instability in transient galvanostatic and potentiostatic modes in a microchannel-nanoslot device
Author(s): R. Abu-Rjal, N. Leibowitz, S. Park, B. Zaltzman, I. Rubinstein, and G. Yossifon
For a sufficiently deep microchannel, both experiments and simulations show a distinct transient nonmonotonic behavior of the system chronopotentiometric and chronoamperometric responses, resulting from the emergence of electroconvective instability in the overlimiting conductance regime.
[Phys. Rev. Fluids 4, 084203] Published Wed Aug 14, 2019
Angular momentum transport and flow organization in Taylor-Couette flow at radius ratio of $η=0.357$
Author(s): Andreas Froitzheim, Sebastian Merbold, Rodolfo Ostilla-Mónico, and Christoph Egbers
Experimental and numerical investigations find that in a wide-gap turbulent Taylor-Couette flow, Nuω features nonconstant effective scaling with ReS due to the curvature-dependent limited capacity of the outer cylinder to emit plumes. For counterrotation, strengthened turbulent Taylor vortices cause a torque maximum at μmax=-0.123.
[Phys. Rev. Fluids 4, 084605] Published Wed Aug 14, 2019
Author(s): Rogelio Valdés, Verónica Angeles, Elsa de la Calleja, and Roberto Zenit
An experimental study of the motion of a self-propelled helix in granular matter shows that there is an optimal pitch angle at which the swimming speed reaches a maximum value. The measurements are compared with predictions with granular resistive force theory, leading to good agreement.
[Phys. Rev. Fluids 4, 084302] Published Tue Aug 13, 2019
Scaling of the production of turbulent kinetic energy and temperature variance in a differentially heated vertical channel
Author(s): Tie Wei
Identity equations are derived for the global turbulent kinetic energy (TKE) and temperature variance production. Shear-produced TKE is found to scale as uτUmax2 and buoyancy-produced TKE scales as uτ2Umax. Scalings for temperature variance production and dissipation are also revealed.
[Phys. Rev. Fluids 4, 081501(R)] Published Mon Aug 12, 2019
Steady flow of one uniformly rotating fluid layer above another immiscible uniformly rotating fluid layer
Author(s): P. D. Weidman and M. R. Turner
We find exact similarity solutions of the Navier-Stokes equations for the steady laminar flow of two immiscible, uniformly rotating fluid layers. For layers which counter-rotate too strongly a self-similar solution does not exist, as given by a condition we find on the angular velocity ratio.
[Phys. Rev. Fluids 4, 084002] Published Mon Aug 12, 2019
Author(s): Wei Huang and Kang Ping Chen
A thermal analysis shows that even without an imposed temperature drop, a gas-expansion-induced transient temperature decrease can slow viscous gas drainage from a semisealed channel with adiabatic walls. At given density drop, gas drains out faster as initial-to-final temperature ratio increases.
[Phys. Rev. Fluids 4, 084202] Published Mon Aug 12, 2019
Author(s): Jiacai Lu and Gretar Tryggvason
Numerical simulations of turbulent multifluid flows, undergoing changes of the interface topology, are carried out using a front-tracking–finite-volume method. The results for varying void fractions show that the flow starts to depart from the bubbly regime at a void fraction of about 15%.
[Phys. Rev. Fluids 4, 084301] Published Mon Aug 12, 2019
Author(s): Taylor S. Geisler, Madhu V. Majji, Jana S. Kesavan, Valerie J. Alstadt, Eric S. G. Shaqfeh, and Gianluca Iaccarino
Large-eddy simulation is used to study turbulent airflow in anatomically accurate rhesus macaque airways along with the transport of microparticles in the flow. Microparticle deposition predictions are compared with model experiments in the same computed-tomography-based airways.
[Phys. Rev. Fluids 4, 083101] Published Fri Aug 09, 2019
Author(s): Jorge Gonzalez-Gutierrez, Salvador Osorio-Ramirez, Francisco J. Solorio-Ordaz, and Roberto Zenit
Laboratory experiments were conducted with synthetic magnetic helical swimmers to study the dynamics of crossing the interface between two immiscible fluids. This system aims to emulate the process through which bacteria are capable of penetrating mucus layers or membranes to cause infections.
[Phys. Rev. Fluids 4, 083102] Published Fri Aug 09, 2019
Vortical and thermal interfacial layers in wall-bounded turbulent flows under transcritical conditions
Author(s): Matthew X. Yao, Zeping Sun, Carlo Scalo, and Jean-Pierre Hickey
Evidence of the presence of vortical and thermal interfacial layers in transcritical turbulent channel flow is presented. These interfaces are tied to the uniform momentum zones. In an analogous manner, uniform thermal zones are defined and characterized in these complex flows.
[Phys. Rev. Fluids 4, 084604] Published Fri Aug 09, 2019
Author(s): Qi Zhou and Peter J. Diamessis
Simulations of large-Reynolds-number stratified wakes reveal dynamics of a strongly stratified regime where thin flow layers form under stratification. Shear instabilities develop between the layers and drive turbulence. The ability to predict whether this novel regime is accessible in a wake of given parameters is demonstrated.
[Phys. Rev. Fluids 4, 084802] Published Fri Aug 09, 2019
Author(s): D. Pettas, G. Karapetsas, Y. Dimakopoulos, and J. Tsamopoulos
Fluid elasticity opposes inertia, creating a static hump and a cusp ahead of it on the film free surface. Nonlinear phenomena, such as resonance of the liquid film with the bottom undulations, are intensified or suppressed by the presence of shear-thinning and elasticity.
[Phys. Rev. Fluids 4, 083303] Published Thu Aug 08, 2019
Viscoelastic film flows over an inclined substrate with sinusoidal topography. II. Linear stability analysis
Author(s): D. Pettas, G. Karapetsas, Y. Dimakopoulos, and J. Tsamopoulos
Stability to linear disturbances of arbitrary wavelength is studied using Floquet theory. Fluid elasticity stabilizes the flow and creates a small window where all disturbances are damped at supercritical conditions. Shear-thinning is destabilizing and may generate disturbances of wavelength shorter than that of the geometry.
[Phys. Rev. Fluids 4, 083304] Published Thu Aug 08, 2019
Author(s): Thomas Cubaud
Hydrodynamic interactions between droplets and high-viscosity fluid threads are investigated in microchannels. A complementary approach is adopted where the thread size is varied for diverse droplet concentrations to help reveal a range of basic fluid structures.
[Phys. Rev. Fluids 4, 084201] Published Thu Aug 08, 2019
Author(s): F. Liu (刘锋), L. P. Lu (陆利蓬), Wouter J. T. Bos, and L. Fang (方乐)
Reversed initial fields can generate nonequilibrium decaying turbulence. During the short time interval when the reversed flow reorganizes to restore its energy cascade, a new dissipation scaling is observed, Cε∼Reλ−2, for a nonequilibrium transient with rapidly evolving dissipation.
[Phys. Rev. Fluids 4, 084603] Published Thu Aug 08, 2019
Author(s): C. M. Mackenzie Dover and K. Sefiane
Contact angle hysteresis is measured on micropillar surfaces with four different area fractions. To fit the data at higher area fractions, the Cassie law is modified to account for capillary bridges.
[Phys. Rev. Fluids 4, 081601(R)] Published Wed Aug 07, 2019
Author(s): Daniel J. Walls, Andrew S. Ylitalo, David S. L. Mui, John M. Frostad, and Gerald G. Fuller
The time-dependent spreading behaviors of a rinsing liquid across a horizontal, rotating substrate pre-coated with thin liquid films is investigated. Four distinct growth behaviors in time of the azimuthally averaged spreading radius are observed and explained with lubrication theory.
[Phys. Rev. Fluids 4, 084102] Published Wed Aug 07, 2019