Latest in physics.flu-dyn

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The energy cascade of surface wave turbulence: toward identifying the active wave couplingFeb 21 2019We investigate experimentally turbulence of surface gravity waves in the Coriolis facility in Grenoble by using both high sensitivity local probes and a time and space resolved stereoscopic reconstruction of the water surface. We show that the water deformation ... More
Lagrangian network analysis of turbulent mixingFeb 21 2019A temporal complex network-based approach is proposed as a novel formulation to investigate turbulent mixing from a Lagrangian viewpoint. By exploiting a spatial proximity criterion, the dynamics of a set of fluid particles is geometrized into a time-varying ... More
Mean flow anisotropy without waves in rotating turbulenceFeb 21 2019We tackle the question of how anisotropy develops in flows subject to background rotation,especially turbulent ones. Inertial waves are generally accepted as the most efficient mechanism to transport energy anisotropically. They have been shown to transfer ... More
On diffusive variants of some classical viscoelastic rate-type modelsFeb 21 2019We present a thermodynamically based approach to the design of models for viscoelastic fluids with stress diffusion effect. In particular, we show how to add a stress diffusion term to some standard viscoelastic rate-type models (Giesekus, FENE-P, Johnson--Segalman, ... More
The evolution of non-linear disturbances in magnetohydrodynamic flowsFeb 21 2019In this article the stability loss of the Hartmann flow are investigated by applying the equations for disturbances. The velocity and electric potential quasi-static MHD model is used. The equations allow us to calculate time-dependent disturbance fields ... More
Experiments on a jet in a crossflow in the low-velocity-ratio regimeFeb 21 2019The hairpin instability of a jet in a crossflow (JICF) for a low jet-to-crossflow velocity ratio is investigated experimentally for a velocity ratio range of $R\in(0.14,0.75)$ and crossflow Reynolds numbers $Re_D\in(260,640)$. From spectral analysis we ... More
The mean conformation tensor in viscoelastic turbulenceFeb 20 2019This work demonstrates that the popular arithmetic mean conformation tensor frequently used in the analysis of turbulent viscoelastic flows is not a good representative of the ensemble. Alternative means based on recent developments in the literature ... More
Curving to fly: Synthetic adaptation unveils optimal flight performance of whirling fruitsFeb 20 2019Appendages of seeds, fruits and other diaspores (dispersal units) are essential for their wind dispersal, as they act as wings and enable them to fly. Whirling fruits generate an auto-gyrating motion from their sepals, a leaf like structure, which curve ... More
Effective rheology of two-phase flow in a capillary fiber bundle modelFeb 20 2019We investigate the effective rheology of two-phase flow in a bundle of parallel capillary tubes carrying two immiscible fluids under an external pressure drop. The diameter of each tube varies along its length and the corresponding capillary threshold ... More
Wave drag on asymmetric bodiesFeb 20 2019An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller wave disturbance moving forwards than backwards, and this is reflected in the wave drag coefficient. This experimental fact is not captured by Michell's theory ... More
Unlikely existence of $k_x^{-1}$ spectral law in wall turbulence: an observation of the atmospheric surface layerFeb 20 2019For wall turbulence, there has been predicted a range of streamwise wavenumbers $k_x$ such that the spectral density of streamwise velocity fluctuations is proportional to $k_x^{-1}$. The existence or nonexistence of this $k_x^{-1}$ law is examined here. ... More
A dynamic closure modeling framework for model order reduction of geophysical flowsFeb 20 2019In this paper, a dynamic closure modeling approach has been derived to stabilize the projection-based reduced order models in the long-term evolution of forced-dissipative dynamical systems. To simplify our derivation without losing generalizability, ... More
Phase-field simulation of core-annular pipe flowFeb 19 2019Phase-field methods have long been used to model the flow of immiscible fluids. Their ability to naturally capture interface topological changes is widely recognized, but their accuracy in simulating flows of real fluids in practical geometries is not ... More
Generalized Rayleigh-Plesset Theory for Cell Size Maintenance in Viruses and BacteriaFeb 19 2019The envelopes covering bacterial cytoplasm possess remarkable elastic properties. They are rigid enough to resist large pressures while being flexible enough to adapt to growth under environmental constraints. Similarly, the virus shells play an important ... More
Circulation in high Reynolds number isotropic turbulence is a bifractalFeb 19 2019The turbulence problem at the level of scaling exponents is hard in part because of the multifractal scaling of small scales, which demands that each moment order be treated and understood independently. This conclusion derives from studies of velocity ... More
Interplay of electro thermo solutal advection and internal electrohydrodynamics governed enhanced evaporation of dropletsFeb 19 2019The article experimentally reveals and theoretically establishes the influence of electric fields on the evaporation kinetics of pendant droplets. It is shown that the evaporation kinetics of saline pendant droplets can be augmented by the application ... More
Interplay of substrate inclination and wettability on droplet impact dynamicsFeb 19 2019Experimental investigations were carried out to elucidate the role of surface wettability and inclination on the post impact dynamics of droplets. Maximum spreading diameter and spreading time were found to decrease with increasing inclination angle and ... More
Start-up flow in shallow deformable microchannelsFeb 19 2019Microfluidic systems are usually fabricated with soft materials that deform due to the fluid stresses. The prediction and control of fluid flow inside these channels thus requires solving fluid-structure interaction problems. Recent experimental and theoretical ... More
pizza: An open-source pseudo-spectral code for spherical quasi-geostrophic convectionFeb 19 2019We present a new pseudo-spectral open-source code nicknamed pizza. It is dedicated to the study of rapidly-rotating Boussinesq convection under the 2-D spherical quasi-geostrophic approximation, a physical hypothesis that is appropriate to model the turbulent ... More
Wave breaking and formation of dispersive shock waves in a defocusing nonlinear optical materialFeb 19 2019We theoretically describe the quasi one-dimensional transverse spreading of a light pulse propagating in a nonlinear optical material in the presence of a uniform background light intensity. For short propagation distances the pulse can be described within ... More
Effect of inertial lift on a spherical particle suspended in flow through a curved ductFeb 19 2019We develop a model of the forces on a spherical particle suspended in flow through a curved duct under the assumption that the particle Reynolds number is small. This extends an asymptotic model of inertial lift force previously developed to study inertial ... More
ECO-like behavior in black hole analoguesFeb 18 2019Classical phenomenological aspects of acoustic perturbations on a draining bathtub geometry where a surface with reflectivity $\mathcal{R}$ is set at a small distance from the would-be acoustic horizon, which is excised, are addressed. A low-frequency ... More
Comparison of the lateral retention forces on sessile, pendant, and inverted sessile dropsFeb 18 2019We compare the lateral retention forces on sessile drops (which are drops that are placed on top of a solid surface), pendant drops (which are drops that are placed on the underside of the surface), and inverted sessile drops (which are drops that are ... More
Energy transfers in MHD turbulence and its applications to dynamoFeb 18 2019In this paper we describe the mode-to-mode energy transfers and energy fluxes of MHD turbulence. These energy transfers are very useful for understanding the turbulence dynamics, as well as for applications such as dynamo. We illustrate how the energy ... More
Contrasting turbulence in stably stratified flows and thermal convectionFeb 18 2019In this paper, the properties of stably stratified turbulence (SST) and turbulent thermal convection are contrasted. A key difference between these flows is the sign of the kinetic energy feed by buoyancy, $\mathcal{F}_B$. For SST, $\mathcal{F}_B < 0$ ... More
Local projection stabilized finite element modeling of viscoelastic two-phase flowsFeb 18 2019A three-field local projection stabilized finite element method is developed for computations of a 3D-axisymmetric buoyancy driven bubble rising in a liquid column in which either the bubble or the liquid column can be viscoelastic. The two-phase flow ... More
Osmosis, from molecular insights to large-scale applicationsFeb 17 2019Osmosis is a universal phenomenon occurring in a broad variety of processes and fields. It is the archetype of entropic forces, both trivial in its fundamental expression - the van 't Hoff perfect gas law - and highly subtle in its physical roots. While ... More
Statistical signature of vortex filaments in classic turbulence: dog or tail?Feb 17 2019The title of this paper echoes the title of a paragraph in the famous book by Frisch on classical turbulence. In the relevant chapter, the author discusses the role of the statistical dynamics of vortex filaments in the fascinating problem of turbulence ... More
Validation of an immersed boundary method for compressible flowsFeb 16 2019This paper sums up some recent validations of an immersed boundary method for compressible flow simulations. It has been already shown that this method is able to provide accurate results without meshing effort around more or less complex geometries. ... More
A fluid mechanic's analysis of the teacup singularityFeb 15 2019The mechanism for singularity formation in an inviscid wall-bounded fluid flow is investigated. The incompressible Euler equations are numerically simulated in a cylindrical container, periodic in the axial coordinate. The flow is axisymmetric with swirl. ... More
Shape-design for stabilizing micro-particles in inertial microfluidic flowsFeb 15 2019Design of microparticles which stabilize at the centerline of a channel flow when part of a dilute suspension is examined numerically for moderate Reynolds numbers ($10 \le Re \le 80$). Stability metrics for particles with arbitrary shapes are formulated ... More
Shape-design for stabilizing micro-particles in inertial microfluidic flowsFeb 15 2019Feb 21 2019Design of microparticles which stabilize at the centerline of a channel flow when part of a dilute suspension is examined numerically for moderate Reynolds numbers ($10 \le Re \le 80$). Stability metrics for particles with arbitrary shapes are formulated ... More
Twente Mass and Heat Transfer Water Tunnel: Temperature controlled turbulent multiphase channel flow with heat and mass transferFeb 15 2019A new vertical water tunnel with global temperature control and the possibility for bubble and local heat & mass injection has been designed and constructed. The new facility offers the possibility to accurately study heat and mass transfer in turbulent ... More
Combined stereoscopic wave mapping and particle image velocimetryFeb 15 2019We describe a technique of image analysis providing the time resolved shape of a water surface simultaneously with the three-component velocity field on this surface. The method relies on a combination of stereoscopic surface mapping and stereoscopic ... More
Hydrodynamics and rheology of a vesicle doublet suspensionFeb 15 2019The dynamics of an adhesive vesicle doublet under various flow conditions is investigated numerically using a high-order, adaptive-in-time boundary integral method. In a quiescent flow, two nearby vesicles move slowly towards each other under the adhesive ... More
Particle-laden thin-film flow in helical channels with arbitrary shallow cross-sectional shapeFeb 14 2019Particle-laden flows in helical channels are of interest for their applications in spiral particle separators used in the mining and mineral processing industries. In this paper, we extend the previous work of Lee, Stokes, Bertozzi (2013) by studying ... More
Super-Resolution Simulation for Real-Time Prediction of Urban MicrometeorologyFeb 14 2019We propose a super-resolution (SR) simulation system that consists of a physics-based meteorological simulation and an SR method based on a deep convolutional neural network (CNN). The CNN is trained using pairs of high-resolution (HR) and low-resolution ... More
Dalton's and Amagat's laws fail in gas mixtures with shock propagationFeb 14 2019As a shock wave propagates through a gas mixture, pressure, temperature, and density increase across the shock front. Rankine-Hugoniot (R-H) relations quantify these changes, correlating post-shock quantities with upstream conditions (pre-shock) and incident ... More
Numerical Simulations of Vorticity Banding of Emulsions in Shear FlowsFeb 14 2019Multiphase shear flows often show banded structures that affect the global behavior of complex fluids e.g. in microdevices. Here we investigate numerically the banding of emulsions, i.e. the formation of regions of high and low volume fraction, alternated ... More
Clustering and energy spectra in two-dimensional dusty gas turbulenceFeb 14 2019We present Direct Numerical Simulation (DNS) of heavy inertial particles (dust) immersed in two-dimensional turbulent flow (gas). The dust are modeled as mono-dispersed heavy particles capable of modifying the flow through two-way coupling. By varying ... More
Condensate in quasi two-dimensional turbulenceFeb 14 2019We investigate the process of formation of large-scale structures in a turbulent flow confined in a thin layer. By means of direct numerical simulations of the Navier-Stokes equations, forced at an intermediate scale, we obtain a split of the energy cascade ... More
Enhanced velocity fluctuations in interacting swimmer suspensionsFeb 14 2019A dilute non-interacting suspension of micro-swimmers exhibits a finite velocity variance and short-ranged correlations that decay over a swimmer length. For a suspension of interacting straight swimmers, however, pair-interactions leads to a non-decaying ... More
Droplets in homogeneous shear turbulenceFeb 14 2019We simulate the flow of two immiscible and incompressible fluids separated by an interface in a homogeneous turbulent shear flow at a shear Reynolds number equal to 15200. The viscosity and density of the two fluids are equal, and various surface tensions ... More
A realizable data-driven approach to delay bypass transition with control theoryFeb 13 2019The current work presents a realizable method to control streaky disturbances in boundary layer flows and delay transition to turbulence via active flow control. Numerical simulations of the nonlinear transitional regime in a Blasius boundary layer are ... More
Nonlinear saturation and oscillations of collisionless zonal flowsFeb 13 2019In homogeneous drift-wave (DW) turbulence, zonal flows (ZFs) can be generated via a modulational instability (MI) that either saturates monotonically or leads to oscillations of the ZF energy at the nonlinear stage. This dynamics is often attributed as ... More
On the role of actuation for the control of streaky structures in boundary layersFeb 13 2019This work deals with the closed-loop control of streaky structures induced by free-stream turbulence in a zero-pressure gradient, transitional boundary layer, by means of localized sensors and actuators. A linear quadratic gaussian regulator is considered ... More
Decoupling of Control and Force Objective in Adjoint-Based Fluid Dynamic Shape OptimizationFeb 13 2019We discuss exterior and classical interior alternatives for evaluating fluid flow induced forces on bodies. The discussion aims at a reduction of the total shape derivative, achieved through a decoupling of control and objective in the exterior approach. ... More
A stochastic approach to the filling dynamics of a porous medium: full/empty pores duality symmetry and the emergence of Darcy's lawFeb 13 2019A stochastic approach to the filling dynamics of an open topology porous structure permeated with a perfectly wetting fluid is presented. From the discrete structure of the disordered voids network with only nearest neighbors links, we derive the "microscopic" ... More
On the classification of incompressible fluids and a mathematical analysis of the equations that govern their motionFeb 13 2019In the first part of the paper we provide a new classification of incompressible fluids characterized by a continuous monotone relation between the velocity gradient and the Cauchy stress. The considered class includes Euler fluids, Navier-Stokes fluids, ... More
A stochastic model for bacteria-driven micro-swimmersFeb 13 2019Experiments have recently shown the feasibility of utilising bacteria as micro-scale robotic devices, with special attention paid to the development of bacteria-driven micro-swimmers taking advantage of built-in actuation and sensing mechanisms of cells. ... More
Steady streaming viscometry of Newtonian liquids in microfluidic devicesFeb 13 2019We report a novel technique capable of measuring the kinematic shear viscosity of Newtonian liquids with steady streaming in microfluidic devices. This probe-free microrheological method utilizes sub-kilohertz liquid oscillation frequencies around a cylindrical ... More
Minimalist shear-driven large scale dynamoFeb 13 2019We show that non-axisymmetric, non-helical perturbations in an unstratified shear flow produce a shear-plane averaged electromotive force (EMF) rigorously proportional to a spatially dependent kinetic helicity. This new "shear-driven $\alpha$-effect" ... More
A new diagnostic tool for water, energy and entropy budgets in climate modelsFeb 12 2019This work presents a novel diagnostic tool for studying the thermodynamics of the climate systems with a wide range of applications, from sensitivity studies to model tuning. It includes a number of modules for assessing the internal energy budget, the ... More
Hydrodynamic and Magnetohydrodynamic Simulations of Wire TurbulenceFeb 12 2019We report on simulations of laboratory experiments in which magnetized supersonic flows are driven through a wire mesh. The goal of the study was to investigate the ability of such a configuration to generate supersonic, MHD turbulence. We first report ... More
A consistent reduction of the two-layer shallow-water equations to an accurate one-layer spreading modelFeb 12 2019The gravity-driven spreading of one fluid in contact with another is of key importance to a range of topics such as oil spills, flow in pipes, and gravity currents. A commonly employed model to describe this phenomenon is the two-layer shallow-water equations, ... More
Dynamics of Hydrogen-Oxygen-Argon Cellular Detonations with a Constant Mean Mass DivergenceFeb 12 2019The present work revisits the problem of modelling the real gaseous detonation dynamics at the macro-scale by simple steady one-dimensional (1D) models. Experiments of detonations propagating in channels with exponentially expanding cross-sections (exponential ... More
Influence of vortex street structure on the efficiency of energy separationFeb 12 2019Regions with reduced and increased values of total enthalpy are observed in a time-averaged flow behind a bluff body. This energy redistribution takes place both in the vortex formation region and in the developed vortex wake. The present paper focuses ... More
Deterministic and stochastic properties of self-similar Rayleigh-Taylor mixing induced by space-varying accelerationFeb 12 2019Rayleigh-Taylor interfacial mixing has critical importance in a broad range of processes in nature and technology. In most instances Rayleigh-Taylor dynamics is induced by variable acceleration, whereas the bulk of existing studies is focused on the cases ... More
Velocity-vorticity correlation and turbulent diffusivity in buoyancy driven fluid dynamicsFeb 12 2019The velocity-vorticity correlation integral (Chkhetiani invariant) is an invariant of a viscous Karman-Howarth equation. In the tree-dimensional space this invariant can naturally determine a turbulent diffusivity (viscosity). It is shown, using results ... More
Velocity-vorticity correlation and turbulent diffusivity in buoyancy driven fluid dynamicsFeb 12 2019Feb 18 2019The velocity-vorticity correlation integral (Chkhetiani invariant) is an invariant of a viscous Karman-Howarth equation. In the tree-dimensional space this invariant can naturally determine a turbulent diffusivity (viscosity). It is shown, using results ... More
Shear jamming and fragility in dense suspensionsFeb 12 2019The phenomenon of shear-induced jamming is a factor in the complex rheological behavior of dense suspensions. Such shear-jammed states are fragile, i.e., they are not stable against applied stresses that are incompatible with the stress imposed to create ... More
Heavy particles in a persistent random flow with trapsFeb 12 2019We study a one-dimensional model for heavy particles in a compressible fluid flow. The flow is modelled by a persistent Gaussian random velocity field, and the heavy particles are assumed to be weakly inertial. Because of its compressibility, the random ... More
Elasto-capillary adhesion: The effect of deformability on adhesion strength and detachmentFeb 12 2019We study the interaction between capillary forces and deformation in the context of a deformable capillary adhesive: a clamped, tense membrane is adhered to a rigid substrate by the surface tension of a liquid droplet. We find that the equilibrium adhesive ... More
Measuring Heat Flux Beyond Fourier's lawFeb 12 2019We use nonequilibrium molecular dynamics (NEMD) to explore the effect of shear flow on heat flux. By simulating a simple fluid in a channel bounded by tethered atoms, the heat flux is computed for two systems: a temperature driven one with no flow and ... More
Variational nonlinear WKB in the Eulerian frameFeb 12 2019Nonlinear WKB is a multiscale technique for studying locally-plane-wave solutions of nonlinear partial differential equations (PDE). Its application comprises two steps: (1) replacement of the original PDE with an extended system separating the large ... More
Surface waves enhance particle dispersionFeb 11 2019We study the horizontal dispersion of passive tracer particles on the free surface of gravity waves in deep water. For random linear waves with the JONSWAP spectrum, the Lagrangian particle trajectories are computed using an exact nonlinear model known ... More
Scaling laws for harmonically trapped two-species mixtures at thermal equilibriumFeb 11 2019We discuss the scaling of the interaction energy with particle numbers for a harmonically trapped two-species mixture at thermal equilibrium experiencing interactions of arbitrary strength and range. In the limit of long-range interactions and weak coupling, ... More
Diffusion of inertia-gravity waves by geostrophic turbulenceFeb 11 2019The scattering of inertia-gravity waves by large-scale geostrophic turbulence in a rapidly rotating, strongly stratified fluid leads to the diffusion of wave energy on the constant-frequency cone in wavenumber space. We derive the corresponding diffusion ... More
Derivation of Pitot corrections for the Zagarola & Smits Superpipe data and their composite fitFeb 11 2019The original turbulent pipe flow experiments in the Princeton "Superpipe" by Zagarola & Smits (1997, 1998) at unprecedented laboratory Reynolds numbers have started an ongoing vigorous debate on the logarithmic law in the mean velocity profile $U^+(y^+)$ ... More
Convergence properties of detonation simulationsFeb 11 2019We present a high-resolution convergence study of detonation initiated by a temperature gradient in a stoichiometric hydrogen-oxygen mixture using the Pencil Code. With Mach numbers reaching 10-30, a certain amount of shock viscosity is needed to remove ... More
Elastic Alfven waves in elastic turbulenceFeb 11 2019Speed of sound waves in gases and liquids is governed by medium compressibility. There exists another type of non-dispersive waves which speed depends on stress instead of medium elasticity. A well-known example is the Alfven wave propagating, with a ... More
Hydrodynamics of electroosmotic flow in a microchannel with porous wallFeb 11 2019Microchannel with porous wall has various microfluidic applications including iontophoresis, diagnostic devices, etc. In order to have an efficient and better design of such devices, exact quantification of velocity field in the microchannel needs to ... More
Stokesian dynamics of pill-shaped Janus particles with stick and slip boundary conditionsFeb 11 2019We study the forces and torques experienced by pill-shaped Janus particles of different aspect ratios where half of the surface obeys the no-slip boundary condition and the other half obeys the Navier slip condition of varying slip lengths. Using a recently ... More
Energy and enstrophy spectra and fluxes for the inertial-dissipation range of two-dimensional turbulenceFeb 10 2019n this paper, using Pao's conjecture [Y.-H. Pao, Phys. Fluids 11, 1371 (1968)], we derive expressions for the spectra and fluxes of kinetic energy and enstrophy for two-dimensional (2D) forced turbulence that extend beyond the inertial range. In these ... More
Asymmetric energy transfers in driven nonequilibrium systems and arrow of timeFeb 10 2019Fundamental interactions are either fully or nearly symmetric under time reversal. But macroscopic phenomena have a definite arrow of time. Though there is no convergence on the origin of time's preferential direction, many researchers believe that the ... More
No net motion for oscillating near-spheres at low Reynolds numbersFeb 10 2019We investigate the flow around an oscillating nearly-spherical particle at low, yet non-vanishing, Reynolds numbers, and the potential resulting locomotion. We analytically demonstrate that no net motion can arise up to order one in Re and order one in ... More
Statistical Lyapunov theory based on bifurcation analysis of energy cascade in isotropic homogeneous turbulence: a physical--mathematical reviewFeb 09 2019This work presents a review of the previous articles dealing with an original turbulence theory proposed by the author, and provides new theoretical insights into some related issues. The new theoretical procedures and methodological approaches confirm ... More
Oscillatory thermocapillary instability of a film heated by a thick substrateFeb 09 2019In this work we consider a new class of oscillatory instabilities that pertain to thermocapillary destabilization of a liquid film heated by a solid substrate. We assume the substrate thickness and substrate-film thermal conductivity ratio are large so ... More
Cavitation and ventilation modalities during ditchingFeb 09 2019The flow taking place in the rear part of the fuselage during the emergency landing on water is investigated experimentally in realistic conditions. To this aim, tests on a double curvature specimen have been performed at horizontal velocities ranging ... More
Is The Starry Night Turbulent?Feb 09 2019Vincent van Gogh's painting, The Starry Night, is an iconic piece of art and cultural history. The painting portrays a night sky full of stars, with eddies (spirals) both large and small. \cite{Kolmogorov1941}'s description of subsonic, incompressible ... More
Is The Starry Night Turbulent?Feb 09 2019Feb 15 2019Vincent van Gogh's painting, The Starry Night, is an iconic piece of art and cultural history. The painting portrays a night sky full of stars, with eddies (spirals) both large and small. \cite{Kolmogorov1941}'s description of subsonic, incompressible ... More
Dynamics of a large population of red blood cells under shear flowFeb 08 2019An exhaustive description of the dynamics under shear flow of a large number of red blood cells in dilute regime is proposed, which highlights and takes into account the dispersion in cell properties within a given blood sample. Physiological suspending ... More
A numerical model based on the curvilinear coordinate system for the MAC method simplifiedFeb 08 2019In this paper we developed a numerical methodology to study some incompressible fluid flows without free surface, using the curvilinear coordinate system and whose edge geometry is constructed via parametrized spline. First, we discussed the representation ... More
Particle Dynamics in Corona Induced Electro-hydrodynamic FlowFeb 08 2019Particle behavior in electro-hydrodynamic (EHD) flow induced by corona discharge is investigated. EHD flow in a point-to-tube corona configuration is studied experimentally and numerically. Multiphysics numerical model couples ion transport equation and ... More
Direct assessment of Kolmogorov's first refined similarity hypothesisFeb 08 2019Using volumetric velocity data from a turbulent laboratory water flow and numerical simulations of homogeneous, isotropic turbulence, we present a direct experimental and numerical assessment of Kolmogorov's first refined similarity hypothesis based on ... More
Boundary regularized integral equation formulation (BRIEF) of Stokes flowFeb 07 2019Single-phase Stokes flow problems with prescribed boundary conditions can be formulated in terms of a boundary regularized integral equation that is completely free of singularities that exist in the traditional formulation. The usual mathematical singularities ... More
DNS-aided explicitly filtered LESFeb 07 2019The equations for LES are formally derived by low-pass filtering the NS equations with the effect of the small scales on the larger ones captured by a SGS model. However, it is known that the LES equations usually employed in practical applications are ... More
Enhanced seepage through a soft porous materialFeb 07 2019We perform direct numerical simulations to study the flow through a model of deformable porous media. For sufficiently soft solid skeleton we find that the flow-rate ($Q$) increases with the pressure-difference ($\Delta P$) at a rate that is faster than ... More
Simulation and Instability Investigation of the Flow around a Cylinder between Two Parallel WallsFeb 07 2019The two-dimensional flows around a cylinder between two parallel walls at Re=40 and Re=100 are simulated with computational fluid dynamics (CFD). The governing equations are Navier-Stokes equations. They are discretized with finite volume method (FVM) ... More
Propulsion and Mixing Generated by the Digitized Gait of Caenorhabditis elegansFeb 06 2019Nematodes have evolved to swim in highly viscous environments. Artificial mechanisms that mimic the locomotory functions of nematodes can be efficient viscous pumps. We experimentally simulate the motion of the head segment of Caenorhabditis elegans by ... More
The vanishing of strong turbulent fronts in bent pipesFeb 06 2019Isolated patches of turbulence in transitional straight pipes are sustained by a strong instability at their upstream front, where the production of turbulent kinetic energy (TKE) is up to five times higher than in the core. Direct numerical simulations ... More
A remark on the zeroth law and instantaneous vortex stretching on the incompressible 3D Euler equationsFeb 06 2019By DNS of Navier-Stokes turbulence, Goto-Saito-Kawahara (2017) showed that turbulence consists of a self-similar hierarchy of anti-parallel pairs of vortex tubes, in particular, stretching in larger-scale strain fields creates smaller-scale vortices. ... More
The role of parasitic modes in nonlinear closure via the resolvent feedback loopFeb 06 2019We use the feedback loop of McKeon \& Sharma (2010), where the nonlinear term in the Navier-Stokes equations is treated as an intrinsic forcing of the linear resolvent operator, to educe the structure of fluctuations in the range of scales (wavenumbers) ... More
Gravitational effect in evaporating binary microdropletsFeb 06 2019The flow in an evaporating glycerol-water binary sub-millimeter droplet with Bond number Bo $\ll$ 1 is studied both experimentally and numerically. First, we measure the flow fields near the substrate by micro-PIV for both sessile and pendant droplets ... More
Wall turbulence with constrained energy extraction from mean flowFeb 05 2019We study the mechanism of energy injection from the mean flow to the fluctuating velocity necessary to maintain wall turbulence. This process is believed to be correctly represented by the linearized Navier--Stokes equations, and three potential linear ... More
Wall turbulence with constrained energy extraction from mean flowFeb 05 2019Feb 13 2019We study the mechanism of energy injection from the mean flow to the fluctuating velocity necessary to maintain wall turbulence. This process is believed to be correctly represented by the linearized Navier--Stokes equations, and three potential linear ... More
Kelvin-Froude wake patterns of a traveling pressure disturbanceFeb 05 2019According to Kelvin, a point pressure source uniformly traveling over the surface of deep calm water leaves behind universal wake pattern confined within $39^{\circ}$ sector and consisting of the so-called transverse and diverging wavefronts. Actual ship ... More
Melt-Blowing of Viscoelastic Jets in Turbulent Airflows: Stochastic Modeling and SimulationFeb 05 2019In melt-blowing processes mico- and nanofibers are produced by the extrusion of polymeric jets into a directed, turbulent high-speed airflow. Up to now the physical mechanism for the drastic jet thinning is not fully understood, since in the existing ... More
Resistive dissipative magnetohydrodynamics from the Boltzmann-Vlasov equationFeb 05 2019We derive the equations of motion of relativistic, resistive, second-order dissipative magnetohydrodynamics from the Boltzmann-Vlasov equation using the method of moments. We thus extend our previous work [Phys. Rev. D 98, 076009 (2018)], where we only ... More
On the fundamentals of Richtmyer-Meshkov dynamics with variable accelerationFeb 04 2019Richtmyer-Meshkov instability (RMI) plays important role in nature and technology, from supernovae and fusion to scramjets and nano-fabrication. Canonical Richtmyer-Meshkov instability is induced by a steady shock and impulsive acceleration, whereas in ... More