# Latest papers in fluid mechanics

### Turbulent/nonturbulent interfaces in high-resolution direct numerical simulation of temporally evolving compressible turbulent boundary layers

Author(s): Xinxian Zhang, Tomoaki Watanabe, and Koji Nagata

Turbulent-nonturbulent interfaces are studied in temporally evolving subsonic and supersonic turbulent boundary layers by comparing the results of direct numerical simulations with the entrainment model based on a single vortex and the theory for spatially evolving boundary layers.

[Phys. Rev. Fluids 3, 094605] Published Tue Sep 18, 2018

### Wake behind a concave curved cylinder

Author(s): Fengjian Jiang, Bjørnar Pettersen, Helge I. Andersson, Jongmin Kim, and Sungtae Kim

The wake behind a concave, curved cylinder configuration is investigated at different Reynolds numbers. Distinctly different wake flow regimes were observed in the computed flow field, including oblique vortex shedding and dislocations. The crucial influence of a straight vertical extension is explored.

[Phys. Rev. Fluids 3, 094804] Published Tue Sep 18, 2018

### Enstrophy spectrum in freely decaying two-dimensional self-similar turbulent flow

Author(s): Igor Vigdorovich

We consider freely decaying two-dimensional homogeneous and isotropic turbulent motion in a self-similar limit that is achieved at large Reynolds numbers based on time and the mean kinetic energy of the flow provided that initial average enstrophy tends to infinity as fluid viscosity tens to zero. I...

[Phys. Rev. E 98, 033110] Published Mon Sep 17, 2018

### Large-eddy simulation and Reynolds-averaged Navier-Stokes modeling of a reacting Rayleigh-Taylor mixing layer in a spherical geometry

Author(s): Brandon E. Morgan, Britton J. Olson, Wolfgang J. Black, and Jacob A. McFarland

Tenth-order compact difference code *Miranda* is used to perform large-eddy simulation (LES) of a hydrogen gas–plastic mixing layer in a spherical geometry. Once the mixing layer has achieved self-similar growth, it is heated to 1 keV, and the second-order arbitrary Lagrangian-Eulerian (ALE) code *Ares*...

[Phys. Rev. E 98, 033111] Published Mon Sep 17, 2018

### Inertia-driven jetting regimes in microfluidic coflows

Author(s): Fan Zhang, Arnaud Erriguible, Théo Gavoille, Michaël T. Timko, and Samuel Marre

Inertial breakup modes are identified at microscale for co-flowing jets using a high-pressure mixer.

[Phys. Rev. Fluids 3, 092201(R)] Published Mon Sep 17, 2018

### Normal shocks with high upstream pressure

Author(s): William A. Sirignano

A normal compressive shock with upstream pressure from 10 to 500 bar is analyzed for density, enthalpy, entropy, and velocity with nitrogen, oxygen, argon, and carbon dioxide. New descriptions for sound speed, Prandtl’s relation, the Rankine-Hugoniot relation, and Riemann invariants are presented.

[Phys. Rev. Fluids 3, 093401] Published Mon Sep 17, 2018

### Visualization and analysis of magnetothermal convection of paramagnetic liquid in the Rayleigh-Benard model

Author(s): Syou Maki, Noriyuki Hirota, and Masayuki Hagiwara

We examined the heat transfer of magnetothermal convection in a Rayleigh-Benard model (height 9.2 mm, vessel diameter 20 mm, aspect ratio 2.17). The working fluid was an aqueous gadolinium nitrate solution of 0.15 mol/kg (pH=4.52 at 305.5 K, paramagnetic substance). Not only the magnetic body force ...

[Phys. Rev. E 98, 033109] Published Wed Sep 12, 2018

### Rayleigh-Taylor turbulence with singular nonuniform initial conditions

Author(s): L. Biferale, G. Boffetta, A. A. Mailybaev, and A. Scagliarini

Three-dimensional direct numerical simulations of Rayleigh-Taylor turbulence with various initial unstable temperature distributions finds a modified self-similar mixing in the long term.

[Phys. Rev. Fluids 3, 092601(R)] Published Wed Sep 12, 2018

### Collisions of drops with an immiscible liquid jet

Author(s): Carole Planchette, Sylvain Petit, Hannes Hinterbichler, and Günter Brenn

The collisions of a drop stream with an immiscible jet are experimentally studied revealing the formation of several complex structures classified in four main regimes. When neither the drops nor the jet fragment,“drops in jet” are observed that could be hardened to produce advanced fibers.

[Phys. Rev. Fluids 3, 093603] Published Wed Sep 12, 2018

### Thermophoresis of Janus particles at large Knudsen numbers

Author(s): Tobias Baier, Sudarshan Tiwari, Samir Shrestha, Axel Klar, and Steffen Hardt

At large Knudsen numbers a Janus particle in a thermal gradient shows a preferred orientation. The interplay between rotational diffusion and thermophoretic motion is investigated.

[Phys. Rev. Fluids 3, 094202] Published Wed Sep 12, 2018

### Shear-induced migration and orientation of rigid fibers in an oscillatory pipe flow

Author(s): Scott Strednak, Saif Shaikh, Jason E. Butler, and Élisabeth Guazzelli

Fibers in suspension migrate towards the center of the pipe where they are more aligned with the flow. The migration depends on the fraction of the volume of the suspension swept out by the rotating fibers.

[Phys. Rev. Fluids 3, 091301(R)] Published Mon Sep 10, 2018

### Forced wakes far from threshold: Stuart-Landau equation applied to experimental data

Author(s): S. Boury, B. Thiria, R. Godoy-Diana, G. Artana, J. E. Wesfreid, and J. D'Adamo

The Stuart-Landau reduced order model is tested with experimental data from the wake of a cylinder wake forced by plasma actuators, finding an important role played by the changing mean flow.

[Phys. Rev. Fluids 3, 091901(R)] Published Mon Sep 10, 2018

### Entrainment model for fully-developed wind farms: Effects of atmospheric stability and an ideal limit for wind farm performance

Author(s): Paolo Luzzatto-Fegiz and Colm-cille P. Caulfield

A new model of wind farm aerodynamics establishes an upper bound for power density, which is an order of magnitude larger than achieved by contemporary turbine arrays. The model also provides a one-equation prediction for the output of existing wind farms, and can include atmospheric stability.

[Phys. Rev. Fluids 3, 093802] Published Mon Sep 10, 2018

### Asymmetric concentration dependence of segregation fluxes in granular flows

Author(s): Ryan P. Jones, Austin B. Isner, Hongyi Xiao, Julio M. Ottino, Paul B. Umbanhowar, and Richard M. Lueptow

Particles differing in size or density segregate in dense granular flows. In bidisperse mixtures, the sinking (small or heavy) species concentration that maximizes the segregation flux is <50% and decreases with increasing size or density ratio, matching a classic kinetic-sieving model.

[Phys. Rev. Fluids 3, 094304] Published Mon Sep 10, 2018

### Extremes, intermittency, and time directionality of atmospheric turbulence at the crossover from production to inertial scales

Author(s): E. Zorzetto, A. D. Bragg, and G. Katul

A study of how the interplay between mechanical and buoyant production of turbulent kinetic energy affects fully developed atmospheric turbulent flows finds impacts both on the frequency of extreme scalar fluctuations and on the time-directional properties of scalar Eulerian measurements.

[Phys. Rev. Fluids 3, 094604] Published Mon Sep 10, 2018

### Linear stability of a contaminated fluid flow down a slippery inclined plane

Author(s): Farooq Ahmad Bhat and Arghya Samanta

The linear stability analysis of a fluid flow down a slippery inclined plane is carried out when the free surface of the fluid is contaminated by a monolayer of insoluble surfactant. The aim is to extend the earlier study [Samanta *et al.*, J. Fluid Mech. **684**, 353 (2011)] for low to high values of the...

[Phys. Rev. E 98, 033108] Published Fri Sep 07, 2018

### Fluidity, anisotropy, and velocity correlations in frictionless, collisional grain flows

Author(s): Diego Berzi and James T. Jenkins

We propose corrections to the kinetic theory for fluidity in granular flows near random close packing, in order to take account of anisotropy and increases in granular temperature.

[Phys. Rev. Fluids 3, 094303] Published Fri Sep 07, 2018

### Statistics of incremental averages of passive scalar fluctuations

Author(s): Colin R. Meyer, Laurent Mydlarski, and Luminita Danaila

An investigation of the statistics of incremental averages of passive scalar fluctuations shows that, unlike statistics of their differences, they inherit information from the scalar field’s large scales, for averages over all increment sizes, and can differ from analogous statistics for the velocity field.

[Phys. Rev. Fluids 3, 094603] Published Fri Sep 07, 2018

### Axially symmetric and latitudinally propagating nonlinear patterns in rotating spherical convection

Author(s): Dali Kong, Keke Zhang, Kameng Lam, and Ashley P. Willis

We report a nonlinear phenomenon discovered in the classical problem of thermal convection in rapidly rotating, self-gravitating, internally heated Boussinesq fluid spheres. When linear convective instability (the most unstable mode of convection) is in the form of an axially symmetric, equatorially...

[Phys. Rev. E 98, 031101(R)] Published Thu Sep 06, 2018

### Turbulence-driven reverse lift on two-dimensional and three-dimensional structures

Author(s): Yaqing Jin, Lin Yan, Haotian Qiu, and Leonardo P. Chamorro

Using laboratory experiments and simplified theoretical arguments, we show that the level of turbulence may reverse the direction of the mean lift on two- and three-dimensional structures with relatively short, deflected splitters. Planar particle image velocimetry and a high-resolution load cell we...

[Phys. Rev. E 98, 033106] Published Thu Sep 06, 2018