We investigate the sedimentation of initially packed paramagnetic particles in the presence of a homogeneous external magnetic field, in a Hele-Shaw cell filled with water. Although the magnetic susceptibility of the particles is small and the particle-particle-induced magnetic interactions are sign...

[Phys. Rev. E 102, 023101] Published Mon Aug 03, 2020

]]>We focus on the self-propelled motion of an oil droplet within an aqueous phase or an aqueous droplet within an oil phase, which originates from an interfacial chemical reaction of surfactant. The droplet motion has been explained by mathematical models, which require the assumption that the chemica...

[Phys. Rev. E 102, 023102] Published Mon Aug 03, 2020

]]>We report the results of simulations of rigid colloidal helices suspended in a shear flow, using dissipative particle dynamics for a coarse-grained representation of the suspending fluid, as well as deterministic trajectories of non-Brownian helices calculated from the resistance tensor derived unde...

[Phys. Rev. E 102, 023103] Published Mon Aug 03, 2020

]]>Heterogeneity and macroscopic anisotropy of porous media play an important role for dilution and reaction enhancement of conservative and reactive plumes. In this study, we perform numerical simulations to investigate steady-state flow and transport in three-dimensional heterogeneous porous media. W...

[Phys. Rev. E 102, 013110] Published Tue Jul 28, 2020

]]>We imaged the pore-scale distribution of air and water within packed columns of glass spheres of different textures using x-ray microcomputed tomography after primary drainage and after secondary imbibition. Postimbibition residual air saturation increases with roughness size. Clusters larger than a...

[Phys. Rev. E 102, 013109] Published Wed Jul 22, 2020

]]>The classical Rayleigh-Bénard convection (RBC) system is known to exhibit either subcritical or supercritical transition to convection in the presence or absence of rotation and/or magnetic field. However, the simultaneous exhibition of subcritical and supercritical branches of convection in plane l...

[Phys. Rev. E 102, 013107] Published Tue Jul 21, 2020

]]>We present three-dimensional measurements of particle-size-dependent acoustophoretic motion of microparticles with diameters from 4.8 $\mu \mathrm{m}$ down to 0.5 $\mu \mathrm{m}$ suspended in either homogeneous or inhomogeneous fluids inside a glass-silicon microchannel and exposed to a standing ultrasound wave. To study the ...

[Phys. Rev. E 102, 013108] Published Tue Jul 21, 2020

]]>The route from linear towards nonlinear and chaotic aerodynamic regimes of a fixed dragonfly wing cross section in gliding flight is investigated numerically using direct Navier-Stokes simulations (DNSs). The dragonfly wing consists of two corrugations combined with a rear arc, which is known to pro...

[Phys. Rev. E 102, 011102(R)] Published Wed Jul 15, 2020

]]>We examine and discuss the spatial evolution of the statistical properties of mechanically generated surface gravity wave fields, initialized with unidirectional spectral energy distributions, uniformly distributed phases, and Rayleigh distributed amplitudes. We demonstrate that nonlinear interactio...

[Phys. Rev. E 102, 013106] Published Wed Jul 15, 2020

]]>The subharmonic acoustic emission of a stable oscillating bubble inside a rigid tube is investigated by direct numerical simulation. The mechanisms of bubble-tube interaction on the acoustic wave emitted by the bubble are clarified. When the bubble is small compared to the tube diameter, a critical ...

[Phys. Rev. E 102, 013105] Published Tue Jul 14, 2020

]]>A walker is a macroscopic coupling of a droplet and a capillary wave field that exhibits several quantumlike properties. In 2009, Eddi *et al.* [Phys. Rev. Lett. **102**, 240401 (2009)] showed that walkers may cross a submerged barrier in an unpredictable manner and named this behavior “unpredictable walk...

[Phys. Rev. E 102, 013104] Published Thu Jul 09, 2020

]]>We demonstrate that functionalizing nanoslits with *p*H-responsive polyelectrolyte brushes can lead to extremely fast electro-osmotic (EOS) water transport, where the maximum centreline velocity and the volume flow rate can be an order of magnitude larger than these quantities in identically charged b...

[Phys. Rev. E 102, 013103] Published Wed Jul 08, 2020

]]>This study reveals that injecting a light fluid of density ${\rho}_{b}$ in the recirculating bubble of a bluff body at $\text{Re}\approx 6.4\times {10}^{4}$ has a greater drag reduction potential than blowing fluid of a density greater than or equal to that of the free stream $\rho $. It is found that the maximum drag reduction scales as ${({\rho}_{b}...}^{}$

[Phys. Rev. E 102, 011101(R)] Published Tue Jul 07, 2020

]]>The focus of this research is to delineate the thermal behavior of a rarefied monatomic gas confined between horizontal hot and cold walls, physically known as rarefied Rayleigh-Bénard (RB) convection. Convection in a rarefied gas appears only for high temperature differences between the horizontal ...

[Phys. Rev. E 102, 013102] Published Tue Jul 07, 2020

]]>Fundamental investigations of how boundary slip relative to the no-slip condition for liquid flow in a set of two distinct idealized pore geometries, i.e., a diverging-converging tortuous pore, in contrast to a straight tube capillary pore, contribute to emergent Darcy flow and flow enhancement are ...

[Phys. Rev. E 102, 013101] Published Mon Jul 06, 2020

]]>Cell motility plays important roles in a range of biological processes, such as reproduction and infections. Studies have hypothesized that the ulcer-causing bacterium *Helicobacter pylori* invades the gastric mucus layer lining the stomach by locally turning nearby gel into sol, thereby enhancing its...

[Phys. Rev. E 101, 063105] Published Tue Jun 30, 2020

]]>We have obtained analytically the complete set of hydrodynamic modes (HMs) for a two-dimensional (2D) fluid confined within a channel with the Navier slip boundary condition at the hydrodynamic boundary. The HMs are orthogonal to each other and hence each represents an independent degree of freedom....

[Phys. Rev. E 101, 063104] Published Mon Jun 22, 2020

]]>A compressible Rayleigh-Taylor (RT) unstable flow with a diffuse interface where the density varies smoothly supports a multiplicity of unstable eigenmodes that grow exponentially in time. This paper studies two relevant problems in a two-dimensional (2-D) RT flow by use of multimode decomposition. ...

[Phys. Rev. E 101, 063103] Published Fri Jun 19, 2020

]]>We study implications of the assumption of power-law dependence of moments of energy dissipation in turbulence on the Reynolds number $\mathrm{Re}$, holding due to intermittency. We demonstrate that at $\mathrm{Re}\to \infty $ the dissipation's logarithm divided by $ln\mathrm{Re}$ converges with probability one to a negative constant. This ...

[Phys. Rev. E 101, 061101(R)] Published Mon Jun 08, 2020

]]>We consider forced small-scale magnetic field advected by an isotropic turbulent flow. The random driving force is assumed to be distributed in a finite region with a scale smaller than the viscous scale of the flow. The two-point correlator is shown to have a stationary limit for any reasonable vel...

[Phys. Rev. E 101, 063102] Published Fri Jun 05, 2020

]]>Random noise in low Reynolds number flow has rarely been used to obtain net migration of microscale objects. In this study, we numerically show that net migration of a microscale object can be extracted from random directional fluid forces in Stokes flow, by introducing deformability and inhomogeneo...

[Phys. Rev. E 101, 063101] Published Wed Jun 03, 2020

]]>We first derive the exact dispersion relation for viscous Rayleigh-Taylor instability in the presence of a horizontal magnetic field using a decomposition method, and we find that the horizontal magnetic field contributes to the generation of vorticity inside the flow, thereby further distorting the...

[Phys. Rev. E 101, 053110] Published Thu May 28, 2020

]]>Scope is the response of Lagrangian flow topologies of three-dimensional time-periodic flows consisting of spheroidal invariant surfaces to perturbation. Such invariant surfaces generically accommodate nonintegrable Hamiltonian dynamics and, in consequence, intrasurface topologies composed of island...

[Phys. Rev. E 101, 053109] Published Wed May 27, 2020

]]>Liquid coating films on solid surfaces exist widely in a plethora of industrial processes. In this study, we focus on the falling of a liquid film on the side surface of a vertical cylinder, where the surface is viewed as slippery, such as a liquid-infused surface. The evolution profiles and flow in...

[Phys. Rev. E 101, 053108] Published Fri May 22, 2020

]]>We present results of numerical and experimental investigations of thermal convection induced by internal heating in both a nonrotating and a rotating spherical gap filled with dielectric fluid. The inner and outer surfaces are maintained at constant temperatures ${T}_{\text{in}}$ and ${T}_{\text{out}}$, respectively. A radial...

[Phys. Rev. E 101, 053106] Published Thu May 21, 2020

]]>Droplets interacting with deformable moving boundaries is ubiquitous. The flexible boundaries may dramatically affect the hydrodynamic behavior of droplets. A numerical method for simulating droplet impact on flexible substrates is developed. The effect of flexibility is investigated. To reduce the ...

[Phys. Rev. E 101, 053107] Published Thu May 21, 2020

]]>Streaming potential mediated pressure driven electrokinetic transport of Phan-Thien–Tanner fluids in a slit type parallel plate microchannel is studied analytically and semianalytically. Without adopting the traditional considerations of Debye–Hückel linearization approximation for low surface poten...

[Phys. Rev. E 101, 053104] Published Mon May 18, 2020

]]>The interplay of inertia and elasticity is shown to have a significant impact on the transport of filamentary objects, modeled by bead-spring chains, in a two-dimensional turbulent flow. We show how elastic interactions among inertial beads result in a nontrivial sampling of the flow, ranging from e...

[Phys. Rev. E 101, 053105] Published Mon May 18, 2020

]]>Wall turbulence has a sublayer where one-point statistics, e.g., the mean velocity and the variances of some velocity fluctuations, vary logarithmically with the distance from the wall. This logarithmic scaling is found here for two-point statistics or specifically two-point cumulants of those fluct...

[Phys. Rev. E 101, 053103] Published Thu May 14, 2020

]]>An integral expression for the translational velocity of a perfectly slipping spherical particle under a time-dependent applied force in unsteady Stokes flow is derived. For example, when the ratio of particle density to fluid density is small, our analysis pertains to an inviscid bubble in a viscou...

[Phys. Rev. E 101, 053102] Published Wed May 13, 2020

]]>We investigate the inviscid compressible flow (Euler) equations constrained by an “isentropic” equation of state (EOS), whose functional form in pressure is an arbitrary function of density alone. Under the aforementioned condition, we interrogate using symmetry methods the scale-invariance of the h...

[Phys. Rev. E 101, 053101] Published Tue May 12, 2020

]]>Rayleigh-Taylor instability (RTI) under radiation background is commonly found in both engineering applications and natural phenomena. In the optically thin and incompressible limit, the corresponding problem can be simplified as an interface discontinuous acceleration (IDA) RTI problem, but to date...

[Phys. Rev. E 101, 043115] Published Thu Apr 30, 2020

]]>Assuming that we wish to measure the surface tension between two liquids by running a pendent drop experiment, we present calculations supporting the case for spinning the drop. For bridges, jets, etc., spinning a heavy fluid surrounded by a lighter fluid is strictly destabilizing. But we find that ...

[Phys. Rev. E 101, 043116] Published Thu Apr 30, 2020

]]>The interaction between the oscillatory boundary-layer flow induced by Faraday waves and a sedimentary granular layer was studied in a Hele-Shaw cell vertically vibrated. The experimental parameters were the vibration frequency $f$ and acceleration $a$ and the particle diameter ${d}_{p}$. At a critical value f...

[Phys. Rev. E 101, 043112] Published Wed Apr 29, 2020

]]>The time-dependent behavior of one-dimensional ion transport into a permselective medium is theoretically modeled in this work for currents exceeding the diffusion limit. Leveraging the findings of Yariv [E. Yariv, Phys. Rev. E **80**, 051201 (2009)], we derive three separate expressions for the potenti...

[Phys. Rev. E 101, 043113] Published Wed Apr 29, 2020

]]>When a droplet impacts on a substrate, the air underneath the droplet is compressed to form an air layer of a dimple shape before the droplet wets the substrate. This air layer is important to the impact dynamics, and many studies have been performed to investigate the air layer during the impact pr...

[Phys. Rev. E 101, 043114] Published Wed Apr 29, 2020

]]>We develop an *adversarial-reinforcement* learning scheme for microswimmers in statistically homogeneous and isotropic turbulent fluid flows, in both two and three dimensions. We show that this scheme allows microswimmers to find nontrivial paths, which enable them to reach a target on average in less...

[Phys. Rev. E 101, 043110] Published Mon Apr 27, 2020

]]>Relaminarization of wall-bounded turbulent flows by means of external static magnetic fields is a long-known phenomenon in the physics of electrically conducting fluids at low magnetic Reynolds numbers. Despite the large literature on the subject, it is not yet completely clear what combination of t...

[Phys. Rev. E 101, 043111] Published Mon Apr 27, 2020

]]>When a water drop impinges on a flat superhydrophobic surface, it bounces off the surface after a certain dwelling time, which is determined by the Rayleigh inertial-capillary timescale. Recent works have demonstrated that this dwelling time (i.e., contact time) is modified on curved superhydrophobi...

[Phys. Rev. E 101, 043108] Published Fri Apr 24, 2020

]]>Uptake of liquid drops into capillary tubes has been experimentally studied and quantitatively analyzed. In experiments, drops of water and aqueous glycerol $(\le 50$ wt %) were drawn into cylindrical borosilicate glass and quartz tubes with an inner diameter of 0.50–0.75 mm. The meniscus height rise was...

[Phys. Rev. E 101, 043109] Published Fri Apr 24, 2020

]]>The linear stability of a Newtonian liquid layer flowing down an inclined plane lined with a deformable linear elastic solid characterized by a continuously varying modulus is analyzed in this study. A low-wave-number asymptotic analysis is performed to obtain an analytical expression for the comple...

[Phys. Rev. E 101, 043107] Published Thu Apr 23, 2020

]]>An important question in turbulent Rayleigh-Bénard convection (RBC) is the effectiveness of convective heat transport, which is conveniently described via the scaling of the Nusselt number ($\mathrm{Nu}$) with the Rayleigh ($\mathrm{Ra}$) and Prandtl ($\mathrm{Pr}$) numbers. In RBC experiments, the heat supplied to the bottom plate...

[Phys. Rev. E 101, 043106] Published Tue Apr 21, 2020

]]>The electroconvective instability (ECI) in an electrodialysis channel under a strong electric field is studied here. The phenomenon of ECI with extreme depletion (ECI-HD) is reported; that is, the overlapping vortices cause the extreme depletion zone to propagate in the horizontal direction. Using s...

[Phys. Rev. E 101, 043105] Published Fri Apr 17, 2020

]]>Collinear velocity relaxation of two spheres immersed in a viscous incompressible fluid is studied on the basis of an approximate expression for the retarded hydrodynamic interaction. After a sudden impulse applied to one sphere, the other one instantaneously starts to move as well, with amplitude d...

[Phys. Rev. E 101, 043103] Published Mon Apr 13, 2020

]]>A turbulent flow mixes in general more rapidly a passive scalar than a laminar flow does. From an energetic point of view, for statistically homogeneous or periodic flows, the laminar regime is more efficient. However, the presence of walls may change this picture. We consider in this investigation ...

[Phys. Rev. E 101, 043104] Published Mon Apr 13, 2020

]]>We demonstrate that the acoustic spin of a first-order Bessel beam can be transferred to a subwavelength (prolate) spheroidal particle at the beam axis in a viscous fluid. The induced radiation torque is proportional to the acoustic spin, which scales with the beam energy density. The analysis of th...

[Phys. Rev. E 101, 043102] Published Tue Apr 07, 2020

]]>The evaporation of a sessile drop in a gaseous environment may be critical to many practical applications. Evaporation dynamics of interacting sessile droplets is strongly influenced by the proximity of adjacent droplets. We study the effects of droplet-droplet vapor-mediated interactions on the eva...

[Phys. Rev. E 101, 043101] Published Wed Apr 01, 2020

]]>We perform equilibrium molecular dynamics simulations for nanoscale fluids confined between two parallel walls and investigate how the autocorrelation function of force acting on one wall is related to the slip length. We demonstrate that for atomically smooth surfaces, the autocorrelation function ...

[Phys. Rev. E 101, 033109] Published Mon Mar 30, 2020

]]>We consider two-dimensional turbulence in the presence of a condensate. The nondiagonal correlation functions of the Lagrangian accelerations are calculated, and it is shown that they have the same universality properties as the nondiagonal correlation functions of the velocity fluctuations.

[Phys. Rev. E 101, 033108] Published Fri Mar 20, 2020

]]>With materials of anisotropic electrical conductivity, it is possible to generate a dynamo with a simple velocity field, of the type precluded by Cowling's theorems with isotropic materials. Following a previous study by Ruderman and Ruzmaikin [M. S. Ruderman and A. A. Ruzmaikin, Magnetic field gene...

[Phys. Rev. E 101, 033107] Published Mon Mar 16, 2020

]]>We report on the enhancement of the hydrodynamic damping of gravity waves at the surface of a fluid layer as they interact with a turbulent vortex flow in a sloshing experiment. Gravity surface waves are excited by oscillating horizontally a square container holding our working fluid (water). At the...

[Phys. Rev. E 101, 033106] Published Thu Mar 12, 2020

]]>We demonstrate that considerable variation of mean Prandtl number ($\mathrm{P}{\mathrm{r}}_{0}$) from unity brings in an additional length scale (called the viscous penetration depth, ${\delta}_{\mathrm{v}}$) into the dynamics of instantaneous as well as time-averaged (mean) flow induced by thermoviscous expansion along a periodically heated so...

[Phys. Rev. E 101, 033105] Published Wed Mar 11, 2020

]]>This study focuses on the three-dimensional (3D) electrohydrodynamic flow instability between two parallel electrodes driven by unipolar charge injection with and without cross flow. Lattice Boltzmann method with a two-relaxation time model is used to compute flow patterns. In the absence of cross f...

[Phys. Rev. E 101, 033103] Published Tue Mar 03, 2020

]]>We use the forced Ostrovsky equation to investigate the generation of internal waves excited by a constant background current flowing over localized topography in the presence of background rotation. As is now well known in the absence of background rotation, the evolution scenarios fall into three ...

[Phys. Rev. E 101, 033104] Published Tue Mar 03, 2020

]]>The evolution of dissolved species in a porous medium is determined by its adsorption on the porous matrix through the classical advection-diffusion processes. The extent to which the adsorption affects the solute propagation in applications related to chromatography and contaminant transport is lar...

[Phys. Rev. E 101, 033101] Published Mon Mar 02, 2020

]]>We study the joint probability distributions of separation $R$ and radial component of the relative velocity ${V}_{R}$ of particles settling under gravity in a turbulent flow. We also obtain the moments of these distributions and analyze their anisotropy using spherical harmonics. We find that the qualitativ...

[Phys. Rev. E 101, 033102] Published Mon Mar 02, 2020

]]>In this paper, the effect of two-frequency modulation of boundary temperatures on the onset of natural convection in a layer of fluid (with Prandtl number $<12.5$) between two vertical parallel planes is considered. The ratio of the two forcing frequencies and the mixing angle for the amplitude of ...

[Phys. Rev. E 101, 023109] Published Wed Feb 26, 2020

]]>We measured the effective diffusion coefficient in regions of microfluidic networks of controlled geometry using the fluorescence recovery after photobleaching (FRAP) technique. The geometry of the networks was based on Voronoi tessellations, and had varying characteristic length scale and porosity....

[Phys. Rev. E 101, 023110] Published Wed Feb 26, 2020

]]>We show that when linear azimuthal perturbations on the surfaces of a fluid shell are regrouped according to ${\alpha}^{m}$, they can be divided into Bell model terms, coupling terms, and the newly identified thin-shell correction terms, where $\alpha $ is the ratio of ${R}_{\text{out}}$ to ${R}_{\text{in}}$, and $m$ is the mode number of a given u...

[Phys. Rev. E 101, 023108] Published Tue Feb 25, 2020

]]>We present a semianalytical theory for the acoustic fields and particle-trapping forces in a viscous fluid inside a capillary tube with arbitrary cross section and ultrasound actuation at the walls. We find that the acoustic fields vary axially on a length scale proportional to the square root of th...

[Phys. Rev. E 101, 023107] Published Thu Feb 20, 2020

]]>We systematically study the effects of liquid viscosity, liquid density, and surface tension on global microbubble coalescence using lattice Boltzmann simulation. The liquid-gas system is characterized by Ohnesorge number $\text{Oh}\equiv {\eta}_{h}/\sqrt{{\rho}_{h}\sigma {r}_{F}}$ with ${\eta}_{h},{\rho}_{h},\sigma $, and ${r}_{F}$ being viscosity and density of liquid, surfac...

[Phys. Rev. E 101, 023106] Published Mon Feb 10, 2020

]]>The three-dimensional dynamics of a single non-Brownian flexible fiber in shear flow is evaluated numerically, in the absence of inertia. A wide range of ratios $A$ of bending to hydrodynamic forces and hundreds of initial configurations are considered. We demonstrate that flexible fibers in shear flo...

[Phys. Rev. E 101, 023104] Published Thu Feb 06, 2020

]]>In this paper, the behavior of a bubble and droplet rising in a system, namely, a dissolved air flotation system, is investigated under different conditions. A lattice Boltzmann model which is based on the Cahn-Hilliard equations for ternary flows is implemented. This model can handle high density a...

[Phys. Rev. E 101, 023105] Published Thu Feb 06, 2020

]]>A Lorenz-like model was set up recently to study the hydrodynamic instabilities in a driven active matter system. This Lorenz model differs from the standard one in that all three equations contain nonlinear terms. The additional nonlinear term comes from the active matter contribution to the stress...

[Phys. Rev. E 101, 023103] Published Wed Feb 05, 2020

]]>The interaction of drops and electric fields occurs in many applications like electrowetting, electrospinning, atomization, but also causes unwanted effects like the aging of high-voltage composite insulators. Water drops are influenced by electric fields due to the polar properties of the water mol...

[Phys. Rev. E 101, 023102] Published Tue Feb 04, 2020

]]>We present a numerical investigation of the effects of gas rarefaction on the energy dynamics of resonating planar nonlinear acoustic waves. The problem setup is a gas-filled, adiabatic tube, excited from one end by a piston oscillating at the fundamental resonant frequency of the tube and closed at...

[Phys. Rev. E 101, 023101] Published Mon Feb 03, 2020

]]>This paper is the continuation of work done in our previous papers [A. A. Doinikov *et al.*, Phys. Rev. E **100**, 033104 (2019); Phys. Rev. E **100**, 033105 (2019)]. The overall aim of the study is to develop a theory for modeling the velocity field of acoustic microstreaming produced by nonspherical oscil...

[Phys. Rev. E 101, 013111] Published Thu Jan 30, 2020

]]>It will be shown that for a solution of salt dissolved in water in contact with a metallic or dielectric wall, the concentration of salt ions (both positive and negative) near the wall can be large enough to exceed the salt's solubility limit, as a result of electrical image charge forces. In additi...

[Phys. Rev. E 101, 013110] Published Wed Jan 29, 2020

]]>A potential source of subharmonic bubble emissions is revealed experimentally by high-speed imaging. When an acoustic bubble is driven at sufficiently large pressure amplitudes, energy transfer from surface to volume oscillations can lead to the triggering of subharmonic spherical oscillations. This...

[Phys. Rev. E 101, 011101(R)] Published Mon Jan 27, 2020

]]>The stability criterion for the magnetic separation of rare-earth ions is studied, taking dysprosium Dy(iii) ions as an example. Emphasis is placed on quantifying the factors that limit the desired high enrichment. During magnetic separation, a layer enriched in Dy(iii) ions is generated via the sur...

[Phys. Rev. E 101, 013109] Published Fri Jan 17, 2020

]]>An analytical theory is developed for acoustic streaming induced by an acoustic wave field inside and outside a spherical fluid particle, which can be a liquid droplet or a gas bubble. The particle is assumed to undergo the monopole (pulsation) and the dipole (translation) oscillation modes. The dis...

[Phys. Rev. E 101, 013108] Published Wed Jan 15, 2020

]]>Direct observation of a rotating detonation engine combustion chamber has enabled the extraction of the kinematics of its detonation waves. These records exhibit a rich set of instabilities and bifurcations arising from the interaction of coherent wave fronts and global gain dynamics. We develop a m...

[Phys. Rev. E 101, 013106] Published Fri Jan 10, 2020

]]>We construct a multifidelity framework for the kinematic parameter optimization of flapping airfoil. We employ multifidelity Gaussian process regression and Bayesian optimization to effectively synthesize the aerodynamic performance of the flapping airfoil with the kinematic parameters under multire...

[Phys. Rev. E 101, 013107] Published Fri Jan 10, 2020

]]>In this work, we model and simulate the shape evolution of critically charged droplets, from the initial spherical shape to the charge emission and back to the spherical shape. The shape deformation is described using the viscous correction for viscous potential flow model, which is a potential flow...

[Phys. Rev. E 101, 013105] Published Thu Jan 09, 2020

]]>In the present paper, we theoretically study the drag force on nanoparticles in the free-molecule regime. It has been widely assumed that the particle temperature is equal to the gas media temperature in the open literature. However, this assumption can be invalid in some real applications. Based on...

[Phys. Rev. E 101, 013103] Published Wed Jan 08, 2020

]]>We consider a formulation for the Hopf functional differential equation which governs statistical solutions of the Navier-Stokes equations. By introducing an exponential operator with a functional derivative, we recast the Hopf equation as an integro-differential functional equation by the Duhamel p...

[Phys. Rev. E 101, 013104] Published Wed Jan 08, 2020

]]>We present a framework for performing input-output system identification near a Hopf bifurcation using data from only the fixed-point branch, prior to the Hopf point itself. The framework models the system with a van der Pol–type equation perturbed by additive noise, and identifies the system parame...

[Phys. Rev. E 101, 013102] Published Mon Jan 06, 2020

]]>A numerical procedure based on the Schwarz-Christoffel map suitable for the study of the Laplacian growth of thin two-dimensional protrusions is presented. The protrusions take the form of either straight needles or curved fingers satisfying Loewner's equation, and are represented by slits in the co...

[Phys. Rev. E 101, 013101] Published Fri Jan 03, 2020

]]>We present a numerical study of inviscid multiple droplet coalescence and break-up under the action of electric forces. Using an embedded potential flow model for the droplet hydrodynamics, coupled with an unbounded exterior electrostatic problem, we are able to perform computations through various ...

[Phys. Rev. E 100, 063111] Published Mon Dec 30, 2019

]]>The rotation of bacterial flagella driven by rotary motors enables the cell to swim through fluid. Bacteria run and reorient by changing the rotational direction of the motor for survival. Fluid environmental conditions also change the course of swimming; for example, cells near a solid boundary dra...

[Phys. Rev. E 100, 063112] Published Mon Dec 30, 2019

]]>With the aid of nondestructive microfocus x-ray computed tomography (CT), we performed three-dimensional (3D) tracer dispersion experiments on randomly unconsolidated packed beds. Plumes of nonreactive sodium iodide solution were point injected into a sodium chloride solvent as a tracer for the eval...

[Phys. Rev. E 100, 063110] Published Thu Dec 26, 2019

]]>We investigate the upper bound on angular momentum transport in Taylor-Couette flow theoretically and numerically by a one-dimensional background field method. The flow is bounded between a rotating inner cylinder of radius ${R}_{i}$ and a fixed outer cylinder of radius ${R}_{o}$. A variational problem is formula...

[Phys. Rev. E 100, 063109] Published Tue Dec 24, 2019

]]>We numerically investigate the contribution of the microstreaming to the acoustic radiation force acting on a small elastic spherical particle placed into an ultrasonic standing wave. When an acoustic wave scatters on a particle the acoustic radiation force and the microstreaming appear as nonlinear...

[Phys. Rev. E 100, 061102(R)] Published Mon Dec 23, 2019

]]>The swimming sperm of many external fertilizing marine organisms face complex fluid flows during their search for egg cells. Aided by chemotaxis, relatively weak flows are known to enhance sperm-egg fertilization rates through hydrodynamic guidance. However, strong flows have the potential to mechan...

[Phys. Rev. E 100, 063107] Published Fri Dec 20, 2019

]]>This work deals with buoyant tracers floating at the ocean surface, where the geostrophic velocity component is two dimensional and rotational (nondivergent) and the ageostrophic component can contain rotational and potential (divergent) contributions that are comparable in size. We consider a rando...

[Phys. Rev. E 100, 063108] Published Fri Dec 20, 2019

]]>The flow and drag induced by active pitching of plates in the wake of a cylinder of diameter $d$ were experimentally studied for various plate lengths $L$ as well as pitching frequencies ${f}_{p}$ and amplitudes ${A}_{0}$ at Reynolds number $\text{Re}=1.6\times {10}^{4}$. Planar particle image velocimetry and a load cell were used to ch...

[Phys. Rev. E 100, 063106] Published Thu Dec 19, 2019

]]>We compare the stochastic closure theory (SCT) to the Townsend-Perry constants as estimated from measurements in the Flow Physic Facility (FPF) at the University of New Hampshire. First, we explain the derivation of the Townsend-Perry constants, which were originally formulated by Meneveau and Marus...

[Phys. Rev. E 100, 061101(R)] Published Mon Dec 16, 2019

]]>A vapor bubble collapsing near a solid boundary in a liquid produces a liquid jet that points toward the boundary. The direction of this jet has been studied for boundaries such as flat planes and parallel walls enclosing a channel. Extending these investigations to enclosed polygonal boundaries, we...

[Phys. Rev. E 100, 063105] Published Fri Dec 13, 2019

]]>The linear theory of the incompressible Rayleigh-Taylor instability in elastic-plastic solid slabs is developed on the basis of the simplest constitutive model consisting in a linear elastic (Hookean) initial stage followed by a rigid-plastic phase. The slab is under the action of a constant acceler...

[Phys. Rev. E 100, 063104] Published Thu Dec 12, 2019

]]>Experiments on vibrated fluids confined in cylindrical and cuboidal containers were performed under the reduced gravity conditions of a parabolic flight. The results constitute a systematic quantitative investigation of the vibroequilibria effect, which refers to the reorientation of vibrated fluids...

[Phys. Rev. E 100, 063103] Published Tue Dec 10, 2019

]]>In this work we studied the differences in flight kinematics and aerodynamics that could relate to differences in wing morphologies of a dragonfly and a damselfly. The damselflies and dragonflies normally fly with the fore wing or hind wing in the lead, respectively. The wing of the damselfly is pet...

[Phys. Rev. E 100, 063102] Published Wed Dec 04, 2019

]]>We find an instability resulting in generation of large-scale vorticity in a fast-rotating small-scale turbulence or turbulent convection with inhomogeneous fluid density along the rotational axis in anelastic approximation. The large-scale instability causes excitation of two modes: (i) the mode wi...

[Phys. Rev. E 100, 063101] Published Mon Dec 02, 2019

]]>A mechanism for the cyclic generation of bursts of magnetic fields by nonlinear torsional flows of complex time dependence but very simple spatial structure is described. These flows were obtained numerically as axisymmetric solutions of convection in internally heated rotating fluid spheres in the ...

[Phys. Rev. E 100, 053110] Published Tue Nov 26, 2019

]]>A temporal analysis of the evolution of Gaussian wave packets in cylindrical capillary jets is presented through both a linear two-mode formulation and a one-dimensional nonlinear numerical scheme. These analyses are normally applicable to arbitrary initial conditions but our study focuses on pure-i...

[Phys. Rev. E 100, 053111] Published Tue Nov 26, 2019

]]>A direction adaptive approach for the reduction of drag and the suppression of lift fluctuation in flow passing a circular cylinder is developed. Flexible filaments are attached to the surface of the cylinder, and different configurations, including the number, lengths, and angles of attachment of t...

[Phys. Rev. E 100, 053107] Published Mon Nov 25, 2019

]]>It is generally accepted that a Worthington jet occurs when a droplet impacts onto a liquid pool. However, in this experimental study of the impact of viscous droplets onto a less-viscous liquid pool, we identify another jet besides the Worthington jet, forming a two-jet phenomenon. The two jets, a ...

[Phys. Rev. E 100, 053108] Published Mon Nov 25, 2019

]]>We study a model for the evolution of an axially symmetric bubble of inviscid fluid in a homogeneous porous medium otherwise saturated with a viscous fluid. The model is a moving boundary problem that is a higher-dimensional analog of Hele-Shaw flow. Here we are concerned with the development of pin...

[Phys. Rev. E 100, 053109] Published Mon Nov 25, 2019

]]>Liquid drops and vibrations are ubiquitous in both everyday life and technology, and their combination can often result in fascinating physical phenomena opening up intriguing opportunities for practical applications in biology, medicine, chemistry, and photonics. Here we study, theoretically and ex...

[Phys. Rev. E 100, 053106] Published Wed Nov 20, 2019

]]>We study numerically the basic flow and linear stability of a capillary jet confined in a rectangular microchannel. We consider both the case where the interface does not touch the solid surfaces and that in which the jet adheres to them with a contact angle slightly smaller than ${180}^{\circ}$. Given an arbi...

[Phys. Rev. E 100, 053104] Published Mon Nov 18, 2019

]]>Under the influence of an external magnetic field **H**, the suspended ferromagnetic particles of a laminar ferrofluid flow try to be oriented along **H** through a relaxation mechanism. Turbulence affects the interaction between the magnetization of each suspended particle and the external field thereby le...

[Phys. Rev. E 100, 053105] Published Mon Nov 18, 2019

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