Physical Review Fluids
External intermittency compensation of dissipation scale distributions in a turbulent boundary layer
Author(s): Sabah F. H. Alhamdi and Sean C. C. Bailey
We investigate the effect of external intermittency on dissipation scales in turbulent boundary layer flow at Reτ≈1000 using a single hot wire probe for one point longitudinal velocity measurements. We find improved scaling universality by accounting for external intermittency throughout the flow.
[Phys. Rev. Fluids 3, 074601] Published Tue Jul 10, 2018
Physics-informed machine learning approach for augmenting turbulence models: A comprehensive framework
Author(s): Jin-Long Wu, Heng Xiao, and Eric Paterson
We present a comprehensive framework for augmenting turbulence models with physics-informed machine learning, illustrating a complete workflow from identification of input/output to prediction of mean velocities. The learned model has Galilean invariance and coordinate rotational invariance.
[Phys. Rev. Fluids 3, 074602] Published Tue Jul 10, 2018
Electrohydrodynamic interaction, deformation, and coalescence of suspended drop pairs at varied angle of incidence
Author(s): Qingming Dong and Amalendu Sau
For a pair of suspended leaky drops, the computed drop velocity (u) with varied permittivity-ratio (εin/εout) and two ‘outflow’ outer vortex pairs drive prolate and oblate deformation mechanisms. Two drops diverge for positive ‘u’ and move closer together and coalesce for negative ‘u’.
[Phys. Rev. Fluids 3, 073701] Published Mon Jul 09, 2018
Author(s): Petter Johansson and Berk Hess
Molecular processes of contact line advancement in dynamic wetting is investigated for no-slip systems using computer simulations. The energy dissipation at the contact line is measured and shown to be large for mesoscopic systems. A model for the dissipation term is proposed.
[Phys. Rev. Fluids 3, 074201] Published Thu Jul 05, 2018
Author(s): Di Li and Xiangchun Xuan
Particles migrate towards the center or walls of a rectangular microchannel if they lead or lag a viscoelastic fluid flow due to positive and negative electrophoresis, respectively. This is opposite to a Newtonian fluid. We attribute this to the shear-induced extra lift in a viscoelastic fluid.
[Phys. Rev. Fluids 3, 074202] Published Thu Jul 05, 2018
Author(s): M. Lebon, J. Sebilleau, and C. Colin
Experiments on air bubbles nucleated on an inclined plate show the importance of the bubble foot shape. A new expression for the capillary force is proposed to predict the bubble detachment diameter.
[Phys. Rev. Fluids 3, 073602] Published Tue Jul 03, 2018
Author(s): R. C. Hidalgo, B. Szabó, K. Gillemot, T. Börzsönyi, and T. Weinhart
Our discrete element simulations and laboratory experiments revealed that density and friction are well-defined functions of the effective inertial number, which fully captures the effect of grain elongation.
[Phys. Rev. Fluids 3, 074301] Published Tue Jul 03, 2018
Author(s): Hannah M. Kittel, Ilia V. Roisman, and Cameron Tropea
Experiments on single drop impacts on thin films of another liquid are analyzed theoretically over 8 orders of magnitude in viscosity ratio νf/νd. Away from νf≊νd we find that the K-numbers determine the splashing threshold and in that region a modified K-number, which we introduce, is needed.
[Phys. Rev. Fluids 3, 073601] Published Mon Jul 02, 2018
Author(s): Masoud Mohammadi-Arzanagh, Saeed Mahdisoltani, Rudolf Podgornik, and Ali Naji
Driving a planar thin film of a compressible viscous fluid using random surface forcing leads to remarkable fluctuation-induced stresses on the bounding surfaces of the film, exhibiting power-law, or even non-decaying, behaviors as a function of the film thickness.
[Phys. Rev. Fluids 3, 064201] Published Fri Jun 29, 2018
Author(s): Hsiang-Ying Chen, Chun-Yu Liu, and Lin I
Experiments find that rogue wave events for Faraday waves tend to be preceded one period before by a surrounding waveform of high angular average and small variation of wave height.
[Phys. Rev. Fluids 3, 064401] Published Thu Jun 28, 2018
Preferential concentration of noninertial buoyant particles in the ocean mixed layer under free convection
Author(s): Tomás Chor, Di Yang, Charles Meneveau, and Marcelo Chamecki
A large eddy simulation is used to study the surface patterns of noninertial passive buoyant particles in the ocean mixed layer. A mechanism for preferential concentration that is independent of inertial effects is then identified and quantified as a function of the terminal rise velocity.
[Phys. Rev. Fluids 3, 064501] Published Thu Jun 28, 2018
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): 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): 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): 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): 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