# Latest papers in fluid mechanics

### Smart inertial particles

Author(s): Simona Colabrese, Kristian Gustavsson, Antonio Celani, and Luca Biferale

A reinforcement learning algorithm is applied to find quasi-optimal policies for buoyancy control of inertial probes/particles in order to avoid trapping and to reach specific regions when navigating in complex two- and three-dimensional flows.

[Phys. Rev. Fluids 3, 084301] Published Mon Aug 06, 2018

### Scale locality of the energy cascade using real space quantities

Author(s): N. A. K. Doan, N. Swaminathan, P. A. Davidson, and M. Tanahashi

Scale locality of the energy cascade is demonstrated using direct numerical simulations data of homogeneous isotropic turbulence with Taylor microscale Reynolds numbers ranging from 37 to 1131. The range of influential scales for this scale locality is found to be independent of Reynolds number.

[Phys. Rev. Fluids 3, 084601] Published Mon Aug 06, 2018

### Inertial spheroids in homogeneous, isotropic turbulence

Author(s): Amal Roy, Anupam Gupta, and Samriddhi Sankar Ray

We study the rotational dynamics of *inertial* disks and rods in three-dimensional, homogeneous, isotropic turbulence. In particular, we show how the alignment and the decorrelation timescales of such spheroids depend, critically, on both the level of inertia and the aspect ratio of these particles. T...

[Phys. Rev. E 98, 021101(R)] Published Fri Aug 03, 2018

### Fluctuation analysis of the atmospheric energy cycle

Author(s): Richard Blender, Denny Gohlke, and Frank Lunkeit

The atmosphere gains available potential energy by solar radiation and dissipates kinetic energy mainly in the atmospheric boundary layer. We analyze the fluctuations of the global mean energy cycle defined by Lorenz in a simulation with a simplified hydrostatic model. The energy current densities a...

[Phys. Rev. E 98, 023101] Published Fri Aug 03, 2018

### Diffusion of self-propelled particles in complex media

Author(s): Juan L. Aragones, Shahrzad Yazdi, and Alfredo Alexander-Katz

An investigation of the behavior of self-propelled particles in complex media finds a transition from thermal diffusion to collision-driven diffusion as the particle area fraction is increased. Collisions with passive particles increases the rotational diffusion of the self-propelled particles, leading to their “self-trapping.”

[Phys. Rev. Fluids 3, 083301] Published Thu Aug 02, 2018

### Angular multiscale statistics of turbulence in a porous bed

Author(s): Xiaoliang He, Sourabh Apte, Kai Schneider, and Benjamin Kadoch

The physics of turbulent flow in porous media is explored in the Lagrangian frame. The evolution of curvature angles along the fluid trajectories reveals the multiscale nature of turbulence. The asymptotic value of the curvature angle quantifies the effect of geometric confinement on turbulence.

[Phys. Rev. Fluids 3, 084501] Published Thu Aug 02, 2018

### Steady thermocapillary migration of a droplet in a uniform temperature gradient combined with a radiation energy source at large Marangoni numbers

Author(s): Zuo-Bing Wu

Steady thermocapillary droplet migration in a uniform temperature gradient combined with a radiation energy source at large Reynolds and Marangoni numbers is studied. To reach a terminal quasisteady process, the magnitude of the radiation energy source is required to preserve the conservative integr...

[Phys. Rev. E 98, 013110] Published Tue Jul 31, 2018

### Mixing mechanism in a two-dimensional bubble column

Author(s): Elise Alméras, Frédéric Risso, Véronique Roig, Cécile Plais, and Frédéric Augier

A large-scale model for transport by secondary open wakes is proposed to describe the spatiotemporal evolution of the concentration field in a homogeneous bidimensional bubble swarm rising at high Reynolds number.

[Phys. Rev. Fluids 3, 074307] Published Tue Jul 31, 2018

### Magnetohydrodynamics- and magnetosolutal-transport-mediated evaporation dynamics in paramagnetic pendant droplets under field stimulus

Author(s): Vivek Jaiswal, Raghvendra Kumar Dwivedi, A. R. Harikrishnan, and Purbarun Dhar

Evaporation kinetics of pendant droplets is an area of immense importance in several applications, in addition to possessing rich fluid dynamics and thermal transport physics. This article experimentally and analytically sheds insight into the augmented evaporation dynamics of paramagnetic pendant d...

[Phys. Rev. E 98, 013109] Published Mon Jul 30, 2018

### Elucidating the mechanism of step emulsification

Author(s): Andrea Montessori, Marco Lauricella, Sauro Succi, Elad Stolovicki, and David Weitz

Three-dimensional Lattice Boltzmann simulations contrast backflow from an external reservoir into a confined microchannel in a dripping mode where the drop breaks off towards the end of the microchannel with a jetting mode at higher flows with drop break off further downstream inside the reservoir.

[Phys. Rev. Fluids 3, 072202(R)] Published Mon Jul 30, 2018

### Delayed coalescence of surfactant containing sessile droplets

Author(s): M. A. Bruning, M. Costalonga, S. Karpitschka, and J. H. Snoeijer

The coalescence of surfactant solutions on a substrate is studied. By varying both the contact angle of the droplets and their difference in surface tension, various regimes with distinct timescales of noncoalescence are identified.

[Phys. Rev. Fluids 3, 073605] Published Mon Jul 30, 2018

### Stratified flows in axially rotating pipes

Author(s): S. Lyu and S. M. Taghavi

There is considerable research to improve the displacement efficiency in buoyant two-fluid flow systems, e.g., when a heavy fluid is injected to displace a light one from a pipe. Experiments show that a pipe rotation helps to completely remove the displaced fluid.

[Phys. Rev. Fluids 3, 074003] Published Mon Jul 30, 2018

### Granular bed consolidation, creep, and armoring under subcritical fluid flow

Author(s): Benjamin Allen and Arshad Kudrolli

Internal imaging shows that a granular bed consolidates and creeps under the action of fluid flow well below the bedload transport critical rate. The bed is shown to be armored with a systematic increase in erosion threshold depending on the duration and strength of applied subcritical shear.

[Phys. Rev. Fluids 3, 074305] Published Mon Jul 30, 2018

### Self-similarity and coarsening rate of a convecting bicontinuous phase separating mixture: Effect of the viscosity contrast

Author(s): Hervé Henry and György Tegze

A computational study shows that the viscosity contrast between the two phases of a multiphase fluid induces noticeable morphological changes to the geometry of the two phases during self-similar coarsening. Quantitative measures are specified.

[Phys. Rev. Fluids 3, 074306] Published Mon Jul 30, 2018

### Thin or bulky: Optimal aspect ratios for ship hulls

Author(s): Jean-Philippe Boucher, Romain Labbé, Christophe Clanet, and Michael Benzaquen

We present a minimal approach to address the problem of ship hull optimization, and compare our theoretical results with existing data. We show that optimal hull aspect ratios result from a subtle balance between wave drag, pressure drag, and skin friction.

[Phys. Rev. Fluids 3, 074802] Published Mon Jul 30, 2018

### Spatial characterization of turbulent channel flow via complex networks

Author(s): G. Iacobello, S. Scarsoglio, J. G. M. Kuerten, and L. Ridolfi

A network-based analysis of a turbulent channel flow numerically solved at Reτ=180 is proposed as an innovative perspective for the spatial characterization of the flow field. Two spatial networks corresponding to the streamwise and wall-normal velocity components are built, where nodes represent po...

[Phys. Rev. E 98, 013107] Published Fri Jul 27, 2018

### Cavitation in a liquid-filled cavity surrounded by an elastic medium: Intercoupling of cavitation events in neighboring cavities

Author(s): Alexander A. Doinikov, Benjamin Dollet, and Philippe Marmottant

The subject of the present theoretical study is the dynamics of a cavitation bubble in a spherical liquid-filled cavity surrounded by an infinite elastic solid. Two objectives are pursued. The first is to derive equations for the velocity and pressure fields throughout the liquid filling the cavity ...

[Phys. Rev. E 98, 013108] Published Fri Jul 27, 2018

### Gas-kinetic simulation of sustained turbulence in minimal Couette flow

Author(s): M. A. Gallis, J. R. Torczynski, N. P. Bitter, T. P. Koehler, S. J. Plimpton, and G. Papadakis

Simulations of a gas in a Minimal Couette unit at Re=500 using Direct Simulation Monte Carlo, a molecular method enforcing molecular chaos for gas-molecule collisions, reproduces the turbulence from DNS. Thus molecular chaos does not prevent development of long-range correlations in turbulence.

[Phys. Rev. Fluids 3, 071402(R)] Published Thu Jul 26, 2018

### Static and dynamic fluid-driven fracturing of adhered elastica

Author(s): Thomasina V. Ball and Jerome A. Neufeld

Transient spreading of a viscous fluid beneath an adhered elastic sheet is controlled by the tip dynamics. Spreading occurs in two dynamical regimes: viscosity dominant and adhesion dominant. Experiments with elastic sheets made of PDMS confirm these regimes and the emergence of a vapor tip.

[Phys. Rev. Fluids 3, 074101] Published Thu Jul 26, 2018

### Spectral energy scaling in precessing turbulence

Author(s): A. Khlifi, A. Salhi, S. Nasraoui, F. Godeferd, and C. Cambon

We study precessing turbulence, which appears in several geophysical and astrophysical systems, by direct numerical simulations of homogeneous turbulence where precessional instability is triggered due to the imposed background flow. We show that the time development of kinetic energy K occurs in tw...

[Phys. Rev. E 98, 011102(R)] Published Wed Jul 25, 2018