Latest papers in fluid mechanics

Intermittent direction reversals of moving spatially localized turbulence observed in two-dimensional Kolmogorov flow

Physical Review E - Mon, 12/18/2017 - 10:00

Author(s): Yoshiki Hiruta and Sadayoshi Toh

We have found that in two-dimensional Kolmogorov flow a spatially localized turbulent state (SLT) exists stably and travels with a constant speed on average switching the moving direction randomly and intermittently for moderate values of the control parameters: Reynolds number and the flow rate. We...

[Phys. Rev. E 96, 063112] Published Mon Dec 18, 2017

Detailed analysis of vibrational nonequilibrium of molecular oxygen in shock-heated flow

Physical Review Fluids - Mon, 12/18/2017 - 10:00

Author(s): Iain D. Boyd and Eswar Josyula

The effectiveness of a widely used phenomenological approach for modeling vibrational excitation is evaluated by comparison with a higher fidelity approach based on an ab initio computational chemistry analysis. A parameter is formulated to predict when the phenomenological approach is inaccurate.

[Phys. Rev. Fluids 2, 123401] Published Mon Dec 18, 2017

Reynolds number scaling of pocket events in the viscous sublayer

Physical Review Fluids - Fri, 12/15/2017 - 10:00

Author(s): M. Metzger, A. Fershtut, C. Kunkel, and J. Klewicki

Pocket events in the viscous sublayer of a turbulent boundary layer are shown to scale with the Taylor microscale. A simple model of a compact vortex propagating obliquely toward the wall from a position near the lower edge of the log layer is consistent with the observed scaling behavior.

[Phys. Rev. Fluids 2, 124602] Published Fri Dec 15, 2017

Relative velocities in bidisperse turbulent suspensions

Physical Review E - Thu, 12/14/2017 - 10:00

Author(s): J. Meibohm, L. Pistone, K. Gustavsson, and B. Mehlig

We investigate the distribution of relative velocities between small heavy particles of different sizes in turbulence by analyzing a statistical model for bidisperse turbulent suspensions, containing particles with two different Stokes numbers. This number, St, is a measure of particle inertia which...

[Phys. Rev. E 96, 061102(R)] Published Thu Dec 14, 2017

Turbulent transport and mixing in transitional Rayleigh-Taylor unstable flow: <i>A priori</i> assessment of gradient-diffusion and similarity modeling

Physical Review E - Thu, 12/14/2017 - 10:00

Author(s): Oleg Schilling and Nicholas J. Mueschke

Data from a 1152×760×1280 direct numerical simulation [N. J. Mueschke and O. Schilling, Phys. Fluids 21, 014106 (2009)] of a Rayleigh-Taylor mixing layer modeled after a small-Atwood-number water-channel experiment is used to investigate the validity of gradient diffusion and similarity closures a p...

[Phys. Rev. E 96, 063111] Published Thu Dec 14, 2017

Modified Taylor vortices

Physical Review Fluids - Thu, 12/14/2017 - 10:00

Author(s): Alejandro G. González and Patrick Weidman

A spatially modulated generalization of Taylor-Green vortices is obtained for Cartesian, polar, and cylindrical systems that are exact analytical solutions of the Navier-Stokes equation. It is shown that a double array of Taylor vortices mapped onto a cylinder may also have radial modulation.

[Phys. Rev. Fluids 2, 124701] Published Thu Dec 14, 2017

Analytical solutions for the profile of two-dimensional droplets with finite-length precursor films

Physical Review E - Wed, 12/13/2017 - 10:00

Author(s): Carlos Alberto Perazzo, J. R. Mac Intyre, and J. M. Gomba

By means of the lubrication approximation we obtain the full family of static bidimensional profiles of a liquid resting on a substrate under partial-wetting conditions imposed by a disjoining-conjoining pressure. We show that for a set of quite general disjoining-conjoining pressure potentials, the...

[Phys. Rev. E 96, 063109] Published Wed Dec 13, 2017

Integral representation of channel flow with interacting particles

Physical Review E - Wed, 12/13/2017 - 10:00

Author(s): Itzhak Fouxon, Zhouyang Ge, Luca Brandt, and Alexander Leshansky

We construct a boundary integral representation for the low-Reynolds-number flow in a channel in the presence of freely suspended particles (or droplets) of arbitrary size and shape. We demonstrate that lubrication theory holds away from the particles at horizontal distances exceeding the channel he...

[Phys. Rev. E 96, 063110] Published Wed Dec 13, 2017

Silo outflow of soft frictionless spheres

Physical Review Fluids - Wed, 12/13/2017 - 10:00

Author(s): Ahmed Ashour, Torsten Trittel, Tamás Börzsönyi, and Ralf Stannarius

Outflow of granular material from containers with small orifices is a ubiquitous phenomenon. A study using hydrogel spheres as templates of soft particles shows that the softness of the grains has considerable consequences: it changes the macroscopic dynamics qualitatively.

[Phys. Rev. Fluids 2, 123302] Published Wed Dec 13, 2017

Lattice Boltzmann heat transfer model for permeable voxels

Physical Review E - Tue, 12/12/2017 - 10:00

Author(s): Gerald G. Pereira, Bisheng Wu, and Shakil Ahmed

We develop a gray-scale lattice Boltzmann (LB) model to study fluid flow combined with heat transfer for flow through porous media where voxels may be partially solid (or void). Heat transfer in rocks may lead to deformation, which in turn can modulate the fluid flow and so has significant contribut...

[Phys. Rev. E 96, 063108] Published Tue Dec 12, 2017

Droplet breakup driven by shear thinning solutions in a microfluidic T-junction

Physical Review Fluids - Mon, 12/11/2017 - 10:00

Author(s): Enrico Chiarello, Anupam Gupta, Giampaolo Mistura, Mauro Sbragaglia, and Matteo Pierno

Droplet breakup in a microfluidic T junction is studied experimentally and numerically (3D) inside continuous phases made of shear-thinning solutions. In squeezing and dripping, the droplet length is found to scale with an effective capillary number, accounting for shear dependent viscosity.

[Phys. Rev. Fluids 2, 123602] Published Mon Dec 11, 2017

From flying wheel to square flow: Dynamics of a flow driven by acoustic forcing

Physical Review Fluids - Fri, 12/08/2017 - 10:00

Author(s): Tristan Cambonie, Brahim Moudjed, Valéry Botton, Daniel Henry, and Hamda Ben Hadid

Acoustic streaming designates the ability to drive flows by acoustic propagation in dissipative fluids. We present an experimental study of a square flow driven by acoustic streaming. The flow evolution from steady to strongly unsteady is characterized, and a transition is observed between two regimes.

[Phys. Rev. Fluids 2, 123901] Published Fri Dec 08, 2017

Statistical characteristics of falling-film flows: A synergistic approach at the crossroads of direct numerical simulations and experiments

Physical Review Fluids - Fri, 12/08/2017 - 10:00

Author(s): Alexandros Charogiannis, Fabian Denner, Berend G. M. van Wachem, Serafim Kalliadasis, and Christos N. Markides

Based on experimental and numerical data from a wide range of flow conditions, relations linking the film-thickness statistics to the bulk-velocity statistics of wavy falling-film flows are developed from a Reynolds decomposition of the local time-varying film thickness and bulk velocity.

[Phys. Rev. Fluids 2, 124002] Published Fri Dec 08, 2017

Asynchronous oscillations of rigid rods drive viscous fluid to swirl

Physical Review Fluids - Fri, 12/08/2017 - 10:00

Author(s): Rintaro Hayashi and Daisuke Takagi

Stokes flow is generated by repeatedly oscillating a pair of rigid rods. Table-top experiments and simulations reveal that a simple phase delay gives rise to complex flow patterns.

[Phys. Rev. Fluids 2, 124101] Published Fri Dec 08, 2017

Poisseuille flow over a wavy surface

Physical Review Fluids - Fri, 12/08/2017 - 10:00

Author(s): Simon J. Haward, Amy Q. Shen, Jacob Page, and Tamer A. Zaki

Experiments on flows through rectangular microchannels with a small amplitude sinusoidal profile on one wall confirm the existence of three regimes of perturbations that depend on the ratio of channel depth to roughness wavelength, α, and the dimensionless viscous length, θ, in agreement with theory.

[Phys. Rev. Fluids 2, 124102] Published Fri Dec 08, 2017

Forced underwater laminar flows with active magnetohydrodynamic metamaterials

Physical Review E - Thu, 12/07/2017 - 10:00

Author(s): Dean Culver and Yaroslav Urzhumov

Theory and practical implementations for wake-free propulsion systems are proposed and proven with computational fluid dynamic modeling. Introduced earlier, the concept of active hydrodynamic metamaterials is advanced by introducing magnetohydrodynamic metamaterials, structures with custom-designed ...

[Phys. Rev. E 96, 063107] Published Thu Dec 07, 2017

Steady film flow over a substrate with rectangular trenches forming air inclusions

Physical Review Fluids - Thu, 12/07/2017 - 10:00

Author(s): S. Varchanis, Y. Dimakopoulos, and J. Tsamopoulos

An analysis of the conditions under which air bubbles may be trapped during the coating of microstructured substrates reveals, among other intriguing observations, that superhydrophobic flow patterns can arise even when the substrate is hydrophilic.

[Phys. Rev. Fluids 2, 124001] Published Thu Dec 07, 2017

Onset of fractional-order thermal convection in porous media

Physical Review E - Wed, 12/06/2017 - 10:00

Author(s): Hamid Karani, Majid Rashtbehesht, Christian Huber, and Richard L. Magin

The macroscopic description of buoyancy-driven thermal convection in porous media is governed by advection-diffusion processes, which in the presence of thermophysical heterogeneities fail to predict the onset of thermal convection and the average rate of heat transfer. This work extends the classic...

[Phys. Rev. E 96, 063105] Published Wed Dec 06, 2017

Effect of an external field on capillary waves in a dipolar fluid

Physical Review E - Wed, 12/06/2017 - 10:00

Author(s): Jason P. Koski, Stan G. Moore, Gary S. Grest, and Mark J. Stevens

The role of an external field on capillary waves at the liquid-vapor interface of a dipolar fluid is investigated using molecular dynamics simulations. For fields parallel to the interface, the interfacial width squared increases linearly with respect to the logarithm of the size of the interface ac...

[Phys. Rev. E 96, 063106] Published Wed Dec 06, 2017

Predicting transition ranges to fully turbulent viscous boundary layers in low Prandtl number convection flows

Physical Review Fluids - Wed, 12/06/2017 - 10:00

Author(s): Janet D. Scheel and Jörg Schumacher

Characteristic properties of turbulent Rayleigh-Bénard convection in the bulk and the boundary layers are summarized for a wide range of Rayleigh and Prandtl numbers, with a specific emphasis on low-Prandtl-number convection.

[Phys. Rev. Fluids 2, 123501] Published Wed Dec 06, 2017


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