Physical Review Fluids

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Fluid particles only separate exponentially in the dissipation range of turbulence after extremely long times

Fri, 03/16/2018 - 10:00

Author(s): Rohit Dhariwal and Andrew D. Bragg

While it is usually assumed that fluid particles separate exponentially in the dissipation range, this need not be true and the evidence for it is controversial. A re-examination of this old problem shows that fluid particles do indeed separate exponentially but only after extremely long times.

[Phys. Rev. Fluids 3, 034604] Published Fri Mar 16, 2018

Technique for forcing high Reynolds number isotropic turbulence in physical space

Fri, 03/16/2018 - 10:00

Author(s): John A. Palmore, Jr. and Olivier Desjardins

Linear forcing is commonly used to simulate isotropic turbulence in physical space. Here we modify the forcing term to act on a low-pass filtered velocity field and obtain a 60% increase of the Taylor microscale Reynolds number on the same mesh. An extension is also made to scalar mixing.

[Phys. Rev. Fluids 3, 034605] Published Fri Mar 16, 2018

Experimental examination of vorticity stripping from a wing-tip vortex in free-stream turbulence

Fri, 03/16/2018 - 10:00

Author(s): Hari C. Ghimire and Sean C. C. Bailey

Circulation loss from a vortex immersed in turbulent surroundings occurs in a nondiffusive manner. Experiments are used to connect the circulation loss to instantaneous instances of vorticity stripping from the vortex core.

[Phys. Rev. Fluids 3, 034702] Published Fri Mar 16, 2018

Non-self-similar viscous gravity currents

Thu, 03/15/2018 - 10:00

Author(s): Bruce R. Sutherland, Kristen Cote, Youn Sub (Dominic) Hong, Luke Steverango, and Chris Surma

Lock-release experiments of viscous gravity currents (VGC) of glycerol released in water find different dynamics from air release. The current advance is nearly constant, then nearly halts as the head flattens, in contrast to known self-similar VGC where the front advances as a 1/5 power of time.

[Phys. Rev. Fluids 3, 034101] Published Thu Mar 15, 2018

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

Thu, 03/15/2018 - 10:00

Author(s): Federico Dalla Barba and Francesco Picano

An investigation of the evaporation of dilute droplets within a turbulent spatial-developing jet via direct numerical simulation is presented. A strong droplet preferential segregation is found, which affects the overall vaporization process and induces a wide spreading of the droplet-size spectrum.

[Phys. Rev. Fluids 3, 034304] Published Thu Mar 15, 2018

Shape dependent phoretic propulsion of slender active particles

Wed, 03/14/2018 - 10:00

Author(s): Y. Ibrahim, R. Golestanian, and T. B. Liverpool

A study of the swimming speed of rodlike self-propelled colloids driven by reactions on their surfaces finds that even for very thin swimmers, cylinders are not the same as ellipsoids with the same aspect ratio. Cylinders swim faster.

[Phys. Rev. Fluids 3, 033101] Published Wed Mar 14, 2018

Experimental observations of the three-dimensional wake structures and dynamics generated by a rigid, bioinspired pitching panel

Wed, 03/14/2018 - 10:00

Author(s): Justin T. King, Rajeev Kumar, and Melissa A. Green

The wake created by a trapezoidal pitching panel displays a variety of dynamics and behaviors. Results show that a chain of highly three-dimensional, alternating vortex rings is shed from the trailing edge. These rings interact with each other in a manner that is dependent on Strouhal number.

[Phys. Rev. Fluids 3, 034701] Published Wed Mar 14, 2018

Bursting dynamics of viscous film without circular symmetry: The effect of confinement

Tue, 03/13/2018 - 10:00

Author(s): Mayuko Murano and Ko Okumura

Experimental observations of bubbles bursting between two confining plates find a constant speed of the rim and a tip that does not grow. The dynamics is governed by surface energy transformed into viscous dissipation. Left and right tip shapes look different due to a difference in focal point.

[Phys. Rev. Fluids 3, 031601(R)] Published Tue Mar 13, 2018

Resistive-force theory for mesh-like superhydrophobic surfaces

Tue, 03/13/2018 - 10:00

Author(s): Ory Schnitzer and Ehud Yariv

A simple leading-order approximation for the slip-length tensor of an arbitrary mesh geometry is obtained in the limit of small solid-fraction of the mesh.

[Phys. Rev. Fluids 3, 032201(R)] Published Tue Mar 13, 2018

Interactions between vortex tubes and magnetic-flux rings at high kinetic and magnetic Reynolds numbers

Tue, 03/13/2018 - 10:00

Author(s): Demosthenes Kivotides

Calculations of interactions between vortex tubes and magnetic rings at high kinetic and magnetic Reynolds numbers indicate that when the Lorentz force dominates plasma inertia there is significant new structure generation that results in similar vorticity and magnetic structure morphologies.

[Phys. Rev. Fluids 3, 033701] Published Tue Mar 13, 2018

Effect of synthetic jet modulation schemes on the reduction of a laminar separation bubble

Mon, 03/12/2018 - 10:00

Author(s): J. H. Seo, F. Cadieux, R. Mittal, E. Deem, and L. Cattafesta

The response of a laminar separation bubble to synthetic jet forcing with various modulation schemes is numerically investigated. The study suggests that the effectiveness of synthetic jet-based flow control could be improved by carefully designing the spectral content of the modulation scheme.

[Phys. Rev. Fluids 3, 033901] Published Mon Mar 12, 2018

Single-particle dispersion in stably stratified turbulence

Mon, 03/12/2018 - 10:00

Author(s): N. E. Sujovolsky, P. D. Mininni, and M. P. Rast

We develop a model for particle dispersion observed in stably stratified flows, such as in the ocean and the nocturnal atmosphere, where turbulence is very efficient at mixing and diffusing transported quantities. The model opens new efficient paths for statistical prediction of particle dispersion.

[Phys. Rev. Fluids 3, 034603] Published Mon Mar 12, 2018

Modeling the effects of small turbulent scales on the drag force for particles below and above the Kolmogorov scale

Fri, 03/09/2018 - 10:00

Author(s): Mikhael Gorokhovski and Rémi Zamansky

A stochastic model is proposed for the response of heavy particles to the small scales of high Reynolds number turbulent flow. Particles below and above the Kolmogorov scale are both considered. In the context of large eddy simulations, this model is assessed by comparison with statistics from direct numerical simulations and experiments.

[Phys. Rev. Fluids 3, 034602] Published Fri Mar 09, 2018

Wake of inertial waves of a horizontal cylinder in horizontal translation

Fri, 03/09/2018 - 10:00

Author(s): Nathanaël Machicoane, Vincent Labarre, Bruno Voisin, Frédéric Moisy, and Pierre-Philippe Cortet

The inertial wave wake of a horizontal cylinder translated horizontally in a fluid rotating about the vertical is analyzed. Results show that, owing to horizontal invariance, the slender-body approximation leads to a quantitative theoretical model of the experimental wake, even for a nonslender body.

[Phys. Rev. Fluids 3, 034801] Published Fri Mar 09, 2018

Universal stability curve for pattern formation in pulsed gas-solid fluidized beds of sandlike particles

Thu, 03/08/2018 - 10:00

Author(s): Lilian de Martín, Coen Ottevanger, J. Ruud van Ommen, and Marc-Olivier Coppens

Granular matter can form regular patterns under periodic excitations, such as ripples on a sandy beach. Pattern formation can also be used to structure the dynamics of a fluidized bed. New experiments show that the pattern stability curve is governed by universal scaling, underpinned by fluid-dynamical fundamentals.

[Phys. Rev. Fluids 3, 034303] Published Thu Mar 08, 2018

Time-dependent particle migration and margination in the pressure-driven channel flow of blood

Wed, 03/07/2018 - 10:00

Author(s): Qin M. Qi and Eric S. G. Shaqfeh

The time evolution of the red blood cell and platelet concentration distributions in pressure-driven flow through a straight channel is studied using a coarse-grained theory with comparison to boundary integral simulations. Key time scales and entrance lengths to reach steady state are reported.

[Phys. Rev. Fluids 3, 034302] Published Wed Mar 07, 2018

Three-dimensional simulations of void collapse in energetic materials

Tue, 03/06/2018 - 10:00

Author(s): Nirmal Kumar Rai and H. S. Udaykumar

We study the dynamics of void collapse and hot spot formation with 3D reactive void collapse simulations for various void shapes. We find that dimensionality plays an important role in hot-spot dynamics, underlining the importance of 3D simulations.

[Phys. Rev. Fluids 3, 033201] Published Tue Mar 06, 2018

Competition between drag and Coulomb interactions in turbulent particle-laden flows using a coupled-fluid–Ewald-summation based approach

Tue, 03/06/2018 - 10:00

Author(s): Yuan Yao and Jesse Capecelatro

A new method is presented for capturing charged inertial particles in turbulence. Numerical simulations show that even in dilute suspensions, particles can self-induce an electric field because of preferential concentration by the particles, resulting in particle agglomeration and enhanced clustering.

[Phys. Rev. Fluids 3, 034301] Published Tue Mar 06, 2018

Contribution of large scale coherence to wind turbine power: A large eddy simulation study in periodic wind farms

Mon, 03/05/2018 - 10:00

Author(s): Tanmoy Chatterjee and Yulia T. Peet

We study massive wind farms with large eddy simultations to improve understanding of wind turbine interaction with atmospheric turbulence. Large scale structures are found to be linked to downdraft mechanisms contributing to turbine power and to modulation of near wall eddies.

[Phys. Rev. Fluids 3, 034601] Published Mon Mar 05, 2018

Role of flexural stiffness of leukocyte microvilli in adhesion dynamics

Thu, 03/01/2018 - 10:00

Author(s): Tai-Hsien Wu and Dewei Qi

Simulations using the Lattice-Boltzmann lattice-spring method (LLM) combined with adhesive dynamics (AD) find that the flexural stiffness of microvilli and their bending deformation have a significant effect on the rolling velocity and on the adhesive forces.

[Phys. Rev. Fluids 3, 031101(R)] Published Thu Mar 01, 2018