Latest papers in fluid mechanics

Swimming sheet near a plane surfactant-laden interface

Physical Review E - Fri, 03/01/2019 - 10:00

Author(s): Vaseem A. Shaik and Arezoo M. Ardekani

In this work we analyze the velocity of a swimming sheet near a plane surfactant-laden interface by assuming the Reynolds number and the sheet's deformation to be small. We observe a nonmonotonic dependence of the sheet's velocity on the Marangoni number (Ma) and the surface Péclet number (Pes). For...

[Phys. Rev. E 99, 033101] Published Fri Mar 01, 2019

Taylor dispersion in the presence of cross flow and interfacial mass transfer

Physical Review Fluids - Fri, 03/01/2019 - 10:00

Author(s): Tiras Y. Lin and Eric S. G. Shaqfeh

A solute flowing in a pressure-driven channel flow experiences an enhanced effective axial dispersion coefficient due to the transverse velocity gradients. An investigation shows how this phenomenon, known as Taylor dispersion, is affected by cross flow and mass transfer at the wall.

[Phys. Rev. Fluids 4, 034501] Published Fri Mar 01, 2019

Analytical calculation of the translational velocity of linked vortices

Physics of Fluids - Fri, 03/01/2019 - 04:04
Physics of Fluids, Volume 31, Issue 3, March 2019.
This paper determines analytically the velocity field induced by a configuration of linked vortices, with the aim of finding the translational velocity of such a configuration. The linked-vortex configuration consists of two vortices; the vortices are thin tubes of circular cross section lying on the surface of an immaterial torus of small aspect ratio [math] (where r1 is the cross section radius of a torus and r0 is its centerline radius). The induced velocity field has been found based on the vector potential associated with the Biot-Savart law by using a multipolar expansion; the comparison of this field with the material condition on the surface of the vortices allows one to calculate the translational velocity. The solution obtained retains effects to first order at the multipolar expansion, which corresponds to the effects the vortex curvature has at the vorticity distribution on its cross section. This solution agrees with the numerical results in the range of 2%. The method presented is generalized to the case of n linked vortices.

Acoustogravitational balance in climbing films

Physical Review Fluids - Thu, 02/28/2019 - 10:00

Author(s): Amihai Horesh, Daniel Khaikin, Mackenzie Karnilaw, Anna Zigelman, and Ofer Manor

In experiments a surface acoustic wave at 20 Mhz propagating down a vertical surface induces a liquid film to climb up the surface against gravity.

[Phys. Rev. Fluids 4, 022001(R)] Published Thu Feb 28, 2019

Numerical investigation of the collapse of a static bubble at the free surface in the presence of neighbors

Physical Review Fluids - Thu, 02/28/2019 - 10:00

Author(s): Digvijay Singh and Arup Kumar Das

Formation of a liquid jet and drop as a consequence of the bursting of a bubble in symmetric and asymmetric neighborhoods is modeled numerically. We find that unbalanced interaction of neighbors forces the jet and drop to bend towards the absent bubbles.

[Phys. Rev. Fluids 4, 023602] Published Thu Feb 28, 2019

Breakup of elongated droplets in microfluidic T-junctions

Physical Review Fluids - Thu, 02/28/2019 - 10:00

Author(s): Cees Haringa, Conrad de Jong, Duong A. Hoang, Luis M. Portela, Chris R. Kleijn, Michiel T. Kreutzer, and Volkert van Steijn

Long droplets entering a microfluidic T-junction get trapped below, and break beyond, a critical capillary number, which is determined theoretically and experimentally in this work.

[Phys. Rev. Fluids 4, 024203] Published Thu Feb 28, 2019

Shock-wave structure according to a linear irreversible thermodynamic model

Physical Review E - Wed, 02/27/2019 - 10:00

Author(s): R. M. Velasco and F. J. Uribe

In this work we present a phenomenological model to look for a better understanding of the shock-wave structure in dilute monatomic gases. The model is based on the principles of linear irreversible thermodynamics, where we have been aware of the flow anisotropy caused by the shock-wave propagation....

[Phys. Rev. E 99, 023114] Published Wed Feb 27, 2019

Self-diffusion in compressible gas flow through a microconduit

Physical Review Fluids - Wed, 02/27/2019 - 10:00

Author(s): Di Shen and Kang Ping Chen

The compressible Navier-Stokes equations already include the self-diffusion effect. Comparisons with 35 experiments show that the self-diffusion effect is too small to account for the mass flow rate enhancement in steady compressible gas flow through a microconduit in the slip flow regime.

[Phys. Rev. Fluids 4, 024202] Published Wed Feb 27, 2019

Low-dimensional representations and anisotropy of model rotor versus porous disk wind turbine arrays

Physical Review Fluids - Wed, 02/27/2019 - 10:00

Author(s): Elizabeth H. Camp and Raúl Bayoán Cal

We experimentally compare wakes within three-bladed rotor and porous disk wind turbine arrays using PIV measurements and proper orthogonal decomposition. Disparities between rotors and disks with important implications for wind turbine simulations is found.

[Phys. Rev. Fluids 4, 024610] Published Wed Feb 27, 2019

No return to reflection symmetry in freely decaying homogeneous turbulence

Physical Review Fluids - Wed, 02/27/2019 - 10:00

Author(s): Katsunori Yoshimatsu and Yukio Kaneda

A certain homogeneous fully developed turbulence, which was initially reflection asymmetric at large scales, is studied theoretically and numerically. It is shown that the turbulence does not relax to any reflection symmetric state, even in the energy containing range.

[Phys. Rev. Fluids 4, 024611] Published Wed Feb 27, 2019

Effect of small inclination on binary convection in elongated rectangular cells

Physical Review E - Tue, 02/26/2019 - 10:00

Author(s): Isabel Mercader, Oriol Batiste, Arantxa Alonso, and Edgar Knobloch

We analyze the effect of a small inclination on the well-studied problem of two-dimensional binary fluid convection in a horizontally extended closed rectangular box with a negative separation ratio, heated from below. The horizontal component of gravity generates a shear flow that replaces the moti...

[Phys. Rev. E 99, 023113] Published Tue Feb 26, 2019

Rayleigh-Taylor convective dissolution in confined porous media

Physical Review Fluids - Tue, 02/26/2019 - 10:00

Author(s): Marco De Paoli, Francesco Zonta, and Alfredo Soldati

RT instability and convection in confined porous media is examined via DNS. Interactions between gravity and diffusion produce efficient fluid mixing, and a superlinear asymptotic growth of the mixing rate is observed and modeled for the first time. Potential geophysical applications are envisioned.

[Phys. Rev. Fluids 4, 023502] Published Tue Feb 26, 2019

Exponential scaling in early-stage agglomeration of adhesive particles in turbulence

Physical Review Fluids - Tue, 02/26/2019 - 10:00

Author(s): Sheng Chen, Shuiqing Li, and Jeffrey S. Marshall

Agglomeration of adhesive particles in turbulence is investigated. The size distribution of early-stage agglomerates follows a unified exponential scaling. A new agglomeration kernel containing information about the fractal structure of agglomerates and the sticking probability is constructed.

[Phys. Rev. Fluids 4, 024304] Published Tue Feb 26, 2019

Experimental study of soft porous lubrication

Physical Review Fluids - Tue, 02/26/2019 - 10:00

Author(s): Zenghao Zhu, Sheldon Weinbaum, and Qianhong Wu

Lessons learned from the motion of red cells in capillaries are applied to a novel experimental study of soft porous lubrication, which conclusively demonstrates a dramatic decrease of friction coefficient with tremendously enhanced pore pressure as a planar board glides over a soft porous layer.

[Phys. Rev. Fluids 4, 024305] Published Tue Feb 26, 2019

Driven active matter: Fluctuations and a hydrodynamic instability

Physical Review Fluids - Tue, 02/26/2019 - 10:00

Author(s): T. R. Kirkpatrick and J. K. Bhattacherjee

A new hydrodynamic instability in driven active matter is discussed. It is similar to the convective instability that occurs in passive fluids, but differs in several important ways. In particular, the transition to turbulence in the active matter system is expected to be novel.

[Phys. Rev. Fluids 4, 024306] Published Tue Feb 26, 2019

Fountain mixing in a filling box at low Reynolds numbers

Physical Review Fluids - Tue, 02/26/2019 - 10:00

Author(s): Nan Xue, Sepideh Khodaparast, and Howard A. Stone

Pouring a liquid down into a container of a denser liquid creates a fountain. We measure the penetration depth of such fountains and characterize the mixing based on the Reynolds (Re) and Froude (Fr) numbers.

[Phys. Rev. Fluids 4, 024501] Published Tue Feb 26, 2019

Exact, approximate, and hybrid treatments of viscous Rayleigh-Taylor and Richtmyer-Meshkov instabilities

Physical Review E - Mon, 02/25/2019 - 10:00

Author(s): Karnig O. Mikaelian

We consider Rayleigh-Taylor and Richtmyer-Meshkov instabilities at the interface between two fluids, one or both of which may be viscous. We derive exact analytic expressions for the amplitude η(t) in the linear regime when only one of the fluids is viscous. The more general case is solved numerical...

[Phys. Rev. E 99, 023112] Published Mon Feb 25, 2019

Multiscale analysis of the structure of homogeneous rotating turbulence

Physical Review Fluids - Mon, 02/25/2019 - 10:00

Author(s): Aurore Naso

Homogeneous rotating turbulence structure is investigated by analyzing instantaneous statistics of the scale-dependent perceived velocity gradient tensor. Rotation is shown to suppress some alignment properties of isotropic turbulence, decreasing enstrophy production and strain production rates.

[Phys. Rev. Fluids 4, 024609] Published Mon Feb 25, 2019

Dynamo effect in decaying helical turbulence

Physical Review Fluids - Fri, 02/22/2019 - 10:00

Author(s): Axel Brandenburg, Tina Kahniashvili, Sayan Mandal, Alberto Roper Pol, Alexander G. Tevzadze, and Tanmay Vachaspati

It is shown that decaying helical turbulence amplifies a weak magnetic field, which then itself becomes helical. However, it displays a transient behavior different from any other helical or nonhelical magnetic decaying field in a parametric representation between the temporal scaling exponents p(t) and q(t).

[Phys. Rev. Fluids 4, 024608] Published Fri Feb 22, 2019

Experiments on the low-Reynolds-number settling of a sphere through a fluid interface

Physical Review Fluids - Wed, 02/20/2019 - 10:00

Author(s): Paul A. Jarvis, Heidy M. Mader, Herbert E. Huppert, Katharine V. Cashman, and Jon D. Blundy

Experiments on the low-Reynolds number settling of a sphere through a fluid interface focus on the effect of the viscosity ratio and Bond number on the shape of the sphere position curve as a function of time, whether sinking occurs through a tailing or film drainage mode and the sinking timescale.

[Phys. Rev. Fluids 4, 024003] Published Wed Feb 20, 2019


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