Latest papers in fluid mechanics

Author(s): Masanari Hattori, Shingo Kosuge, and Kazuo Aoki

The slip boundary conditions for the compressible Navier-Stokes equations for a polyatomic gas are derived from kinetic theory using the ellipsoidal statistical model of the Boltzmann equation. The slip coefficients for some typical polyatomic gases are presented explicitly.

[Phys. Rev. Fluids 3, 063401] Published Wed Jun 27, 2018

Author(s): Ö. D. Gürcan

A nested polyhedra model has been developed for magnetohydrodynamic turbulence. Driving only the velocity field at large scales with random, divergence-free forcing results in a clear, stationary k−5/3 spectrum for both kinetic and magnetic energies. Since the model naturally effaces disparate scale...

[Phys. Rev. E 97, 063111] Published Tue Jun 26, 2018

Author(s): Shuyue Lai, Ryan W. Houim, and Elaine S. Oran

A continuum granular model is used to investigate dust dispersion and segregation behind a moving shock in a polydispersed system. The results indicate that larger and heavier particles are more dispersed than smaller and lighter ones. The reasons are discussed in terms of the governing forces.

[Phys. Rev. Fluids 3, 064306] Published Tue Jun 26, 2018

Author(s): G. Almondo, J. Einarsson, J. R. Angilella, and B. Mehlig

We calculate, by numerical simulation of a Langevin equation, how the intrinsic viscosity of a dilute suspension of small (triaxial) ellipsoids depends on the degree to which triaxiality is broken. We find that the intrinsic viscosity decreases as the shape becomes less axisymmetric.

[Phys. Rev. Fluids 3, 064307] Published Tue Jun 26, 2018

Author(s): Martin James, Wouter J. T. Bos, and Michael Wilczek

A minimal continuum model for active fluids exhibits turbulence as well as a dynamic hexagonal vortex lattice state, which is preceded by an extended turbulent transient.

[Phys. Rev. Fluids 3, 061101(R)] Published Mon Jun 25, 2018

Author(s): K. Sandeep Reddy, Stephan Fauve, and Christophe Gissinger

A numerical study shows that an electrically conducting fluid driven by a traveling magnetic field always exhibits a Joule dissipation larger than the viscous one. This surprising result suggests the existence of an upper bound for the efficiency of electromagnetic pumps, which can’t exceed 50%.

[Phys. Rev. Fluids 3, 063703] Published Mon Jun 25, 2018

Author(s): Brian Mastracci and Wei Guo

Particle tracking velocimetry is applied to thermal counterflow in superfluid helium (He II), and the first method for separately analyzing the normal fluid and quantized vortex tangle velocities is presented, opening the door to new quantitative measurements of quantum turbulence.

[Phys. Rev. Fluids 3, 063304] Published Fri Jun 22, 2018

Author(s): Kyle J. Caspary, Dahan Choi, Fatima Ebrahimi, Erik P. Gilson, Jeremy Goodman, and Hantao Ji

The effects of axial boundary conductivity on the formation and stability of a magnetized free Stewartson-Shercliff layer (SSL) in a short Taylor-Couette device are reported. As the axial field increases with insulating endcaps, hydrodynamic Kelvin-Helmholtz-type instabilities set in at the SSLs of ...

[Phys. Rev. E 97, 063110] Published Wed Jun 20, 2018

Author(s): Giovanniantonio Natale, Naveen K. Reddy, Robert K. Prud'homme, and Jan Vermant

Orientation dynamics of graphene suspensions is investigated in oscillatory shear flow via flow dichroism. To evaluate whether graphene sheets behave as flexible or rigid sheets during flow, the experimental data are compared with predictions from a single particle Smoluchowski equation for spheroids.

[Phys. Rev. Fluids 3, 063303] Published Wed Jun 20, 2018

Author(s): Y. B. Sun, J. J. Tao, and X. T. He

In the previous studies of Rayleigh-Taylor instability, different methods were used to consider the effects of elasticity, viscosity, and magnetic fields. In this paper, a unified method, which was first used for fluids, is validated for different physical models, where the unstable mode is decompos...

[Phys. Rev. E 97, 063109] Published Tue Jun 19, 2018

Author(s): I. Grants and G. Gerbeth

Combined static and alternating magnetic fields are shown to create an oscillating pressure that can cause cavitation in molten metals. A time-averaged flow is also excited, consisting of two tori squeezed to thin boundary layers. Flow instability develops as a standing wave between these tori.

[Phys. Rev. Fluids 3, 063902] Published Tue Jun 19, 2018

Author(s): Kim M. J. Alards, Hadi Rajaei, Rudie P. J. Kunnen, Federico Toschi, and Herman J. H. Clercx

The angle of directional change of tracer trajectories in rotating Rayleigh-Bénard convection is studied as a function of the time increment τ between two instants of time along the trajectories, both experimentally and with direct numerical simulations. Our aim is to explore the geometrical charact...

[Phys. Rev. E 97, 063105] Published Mon Jun 18, 2018

Author(s): Binita Nath, Gautam Biswas, Amaresh Dalal, and Kirti Chandra Sahu

The present study focuses on the cross-stream migration of a neutrally buoyant two-dimensional drop in a Poiseuille flow in a channel under the influence of an electric field. In the absence of an electric field, the important nondimensional parameters describing this problem are the viscosity ratio...

[Phys. Rev. E 97, 063106] Published Mon Jun 18, 2018

Author(s): Aditya G. Nair, Steven L. Brunton, and Kunihiko Taira

A networked-oscillator-based analysis is performed to examine and control the transfer of kinetic energy for periodic bluff body flows. The dynamics of energy fluctuations in the flow field are described by a set of oscillators defined by conjugate pairs of spatial proper orthogonal decomposition (P...

[Phys. Rev. E 97, 063107] Published Mon Jun 18, 2018

Author(s): Egor Yushkov, Alexander Lukin, and Dmitry Sokoloff

We study average magnetic field growth in a mirror-symmetrical Kazantsev turbulent flow near the dissipative scales. Our main attention is directed to a subcritical regime, when an exponential decrease of magnetic energy is usually expected. We show that instead of damping, transient energy growth c...

[Phys. Rev. E 97, 063108] Published Mon Jun 18, 2018

Author(s): Thomas D. Montenegro-Johnson

Janus-like rods which can be externally switched between straight, U, and S shapes give the possibility of steering individual rods within a group through a complex geometry.

[Phys. Rev. Fluids 3, 062201(R)] Published Mon Jun 18, 2018

Author(s): Santosh Hemchandra, Santosh Shanbhogue, Seunghyuck Hong, and Ahmed F. Ghoniem

With numerical methods and analysis of existing experimental results we show that combustion instability in a backward-facing step combustor can be maintained either with weak coupling between acoustic and hydrodynamic modes (semi-open loop) or with strong coupling (fully closed loop).

[Phys. Rev. Fluids 3, 063201] Published Mon Jun 18, 2018

Author(s): P. K. Yeung, K. R. Sreenivasan, and S. B. Pope

A study combining spectral filtering and numerical simulations at enhanced spatial and/or temporal resolution is used to clarify the proper scaling of dissipation and enstrophy in forced incompressible isotropic turbulence.

[Phys. Rev. Fluids 3, 064603] Published Mon Jun 18, 2018

Author(s): Benjamin Cross, Chloé Barraud, Cyril Picard, Liliane Léger, Frédéric Restagno, and Élisabeth Charlaix

Experiments with a complex fluid in an oscillating atomic force microscope find that the wall slip is well characterised by a real Navier interfacial friction coefficient instead of the usual slip height.

[Phys. Rev. Fluids 3, 062001(R)] Published Fri Jun 15, 2018

Author(s): Andrew M. Fiore, Gang Wang, and James W. Swan

Immersed boundary simulations are used to study settling in dispersions of sticky colloids and to develop an empirical model for the settling rate that is in good agreement with experiments. The model is applied to characterize attractive interactions in concentrated macromolecular solutions.

[Phys. Rev. Fluids 3, 063302] Published Fri Jun 15, 2018