Latest papers in fluid mechanics

Edge states control droplet breakup in subcritical extensional flows

Physical Review Fluids - Wed, 07/18/2018 - 11:00

Author(s): Giacomo Gallino, Tobias M. Schneider, and François Gallaire

We examine theoretically the break-up dynamics of a droplet in a sub-critical extensional flow. We find that it is analogous to other nonlinear dynamical systems with a finite basin of attraction, being governed by an unstable edge state equilibrium in the basin boundary of the base state.


[Phys. Rev. Fluids 3, 073603] Published Wed Jul 18, 2018

Drag coefficient and flow structure downstream of mangrove root-type models through PIV and direct force measurements

Physical Review Fluids - Wed, 07/18/2018 - 11:00

Author(s): Amirkhosro Kazemi, Keith Van de Riet, and Oscar M. Curet

The drag coefficient of mangrove roots reveals a dependency on porosity and Reynolds number. By introducing the effective diameter via streamwise velocity and vortex shedding frequency, the effective drag coefficient of the root model can be predicted from a universal curve fit.


[Phys. Rev. Fluids 3, 073801] Published Wed Jul 18, 2018

Control of Rayleigh-Taylor instability onset time and convective velocity by differential diffusion effects

Physical Review E - Tue, 07/17/2018 - 11:00

Author(s): S. S. Gopalakrishnan, J. Carballido-Landeira, B. Knaepen, and A. De Wit

Fingering instabilities of a miscible interface between two fluids in a gravitational field can develop due to adverse density gradients as in the well-known Rayleigh-Taylor (RT) and double-diffusive (DD) instabilities. In the absence of differential diffusion, the mixing rate and the onset time of ...


[Phys. Rev. E 98, 011101(R)] Published Tue Jul 17, 2018

Influence of capillarity and gravity on confined Faraday waves

Physical Review Fluids - Tue, 07/17/2018 - 11:00

Author(s): S. V. Diwakar, Vibhor Jajoo, Sakir Amiroudine, Satoshi Matsumoto, Ranga Narayanan, and Farzam Zoueshtiagh

The dual roles of gravity and interfacial tension are experimentally studied. The existence of a crossover frequency, on either side of which gravity plays opposing roles, is confirmed. Faraday waves show a surprising stabilization with the reduction in interfacial tension.


[Phys. Rev. Fluids 3, 073902] Published Tue Jul 17, 2018

Microscopic investigation of vortex breakdown in a dividing T-junction flow

Physical Review Fluids - Mon, 07/16/2018 - 11:00

Author(s): San To Chan, Simon J. Haward, and Amy Q. Shen

A clear visualization of vortex breakdown is captured in a dividing microfluidic T-junction flow. This eye-catching structure can be greatly altered by slight outflow imbalances. Our results will guide the use of vortex breakdown to enhance flow control in lab-on-a-chip devices.


[Phys. Rev. Fluids 3, 072201(R)] Published Mon Jul 16, 2018

Optimized kinematics enable both aerial and aquatic propulsion from a single three-dimensional flapping wing

Physical Review Fluids - Mon, 07/16/2018 - 11:00

Author(s): Jacob S. Izraelevitz, Miranda Kotidis, and Michael S. Triantafyllou

Experiments on a prototype flapping robotic wing show that a single design can propel in both air and water, as do puffins and other auks, by varying wing kinematics. We optimize for each fluid with a force measurement feedback scheme and determine the unsteady wakes through dye visualization.


[Phys. Rev. Fluids 3, 073102] Published Mon Jul 16, 2018

Pore-scale statistics of flow and transport through porous media

Physical Review E - Fri, 07/13/2018 - 11:00

Author(s): Soroush Aramideh, Pavlos P. Vlachos, and Arezoo M. Ardekani

Flow in porous media is known to be largely affected by pore morphology. In this work, we investigate the effects of pore geometry on the transport and spatial correlations of flow through porous media in two distinct pore structures arising from three-dimensional assemblies of overlapping and nonov...


[Phys. Rev. E 98, 013104] Published Fri Jul 13, 2018

Growth of liquid-gas interfacial perturbations driven by acoustic waves

Physical Review Fluids - Fri, 07/13/2018 - 11:00

Author(s): Brandon Patterson and Eric Johnsen

Motivated by ultrasound-induced pulmonary hemorrhage, we computationally study acoustic waves in water interacting with a perturbed water-air interface. We demonstrate that baroclinic vorticity due to the misaligned pressure (waves) and density (interface) gradients drives the perturbation growth.


[Phys. Rev. Fluids 3, 074002] Published Fri Jul 13, 2018

Segregation of large particles in dense granular flows suggests a granular Saffman effect

Physical Review Fluids - Fri, 07/13/2018 - 11:00

Author(s): K. van der Vaart, M. P. van Schrojenstein Lantman, T. Weinhart, S. Luding, C. Ancey, and A. R. Thornton

What causes the rising or segregation of large particles at very low concentrations in dense bidisperse granular flows? The scaling of the lift force experienced by large particles with their downstream velocity lag suggests that the answer is a granular equivalent of the Saffman effect.


[Phys. Rev. Fluids 3, 074303] Published Fri Jul 13, 2018

Coherent structures in a screen cylinder wake

Physical Review Fluids - Fri, 07/13/2018 - 11:00

Author(s): Azlin Mohd Azmi, Tongming Zhou, Yu Zhou, Hanfeng Wang, and Liang Cheng

While the solid cylinder wake shows apparent and stable shedding frequency, the screen cylinder wake shows a broad-band peak with a trend of decreasing frequency, indicating that amalgamation of vortices has taken place. This trend implies that the merging process does not occur at a fixed location.


[Phys. Rev. Fluids 3, 074702] Published Fri Jul 13, 2018

Acoustic detection of electrostatic suppression of the Leidenfrost state

Physical Review E - Thu, 07/12/2018 - 11:00

Author(s): Arjang Shahriari, Preston S. Wilson, and Vaibhav Bahadur

At high temperatures, a droplet can rest on a cushion of its vapor (the Leidenfrost effect). Application of an electric field across the vapor gap fundamentally eliminates the Leidenfrost state by attracting liquid towards the surface. This study uses acoustic signature tracking to study electrostat...


[Phys. Rev. E 98, 013103] Published Thu Jul 12, 2018

Vorticity fluxes and secondary flow: Relevance for turbulence modeling

Physical Review Fluids - Thu, 07/12/2018 - 11:00

Author(s): A. Vidal, H. M. Nagib, and R. Vinuesa

Direct numercal simulations of fully developed turbulence in a rectangular duct are used to study the fluxes of vorticity.


[Phys. Rev. Fluids 3, 072602(R)] Published Thu Jul 12, 2018

Global stability of flowing red blood cell trains

Physical Review Fluids - Thu, 07/12/2018 - 11:00

Author(s): Spencer H. Bryngelson and Jonathan B. Freund

Flowing trains of red blood cells are stable when tightly confined but can otherwise break down into an irregular flow. A linear stability formulation is developed to analyze this biological phenomena, advancing understanding of its origin and guiding the design of devices that process blood cells.


[Phys. Rev. Fluids 3, 073101] Published Thu Jul 12, 2018

Shear fronts in shear-thickening suspensions

Physical Review Fluids - Wed, 07/11/2018 - 11:00

Author(s): Endao Han, Matthieu Wyart, Ivo R. Peters, and Heinrich M. Jaeger

Snapshot of a propagating shear front that transforms a dense suspension from a fluid into a jammed, solid-like state. A comprehensive description of this transformation is developed, which links the transient dynamics to parameters obtainable from steady-state rheology.


[Phys. Rev. Fluids 3, 073301] Published Wed Jul 11, 2018

Resolvent analysis of separated and attached flows around an airfoil at transitional Reynolds number

Physical Review Fluids - Wed, 07/11/2018 - 11:00

Author(s): Nikitas Thomareis and George Papadakis

Cross-stream component of the optimal response at the natural shear layer frequency (solid black line: displacement thickness of the boundary layer, solid brown line: zero-streamwise mean velocity contour).


[Phys. Rev. Fluids 3, 073901] Published Wed Jul 11, 2018

Minimum size for the top jet drop from a bursting bubble

Physical Review Fluids - Wed, 07/11/2018 - 11:00

Author(s): C. Frederik Brasz, Casey T. Bartlett, Peter L. L. Walls, Elena G. Flynn, Yingxian Estella Yu, and James C. Bird

High-speed imaging experiments and numerical simulations show that the minimum size of drops ejected after bubble bursting is determined by an interplay of viscous and inertial-capillary forces both prior and subsequent to jet formation. Implications for sea spray aerosol generation are discussed.


[Phys. Rev. Fluids 3, 074001] Published Wed Jul 11, 2018

Clogging at pore scale and pressure-induced erosion

Physical Review Fluids - Wed, 07/11/2018 - 11:00

Author(s): R. Jäger, M. Mendoza, and H. J. Herrmann

Using a coupled lattice Boltzmann method/discrete element method model, the clogging of a pore with particles at microscopic scale is studied. We show that erosive bursts occur when the hydraulic pressure exceeds a critical point, which depends on the adhesive forces and the pores’ geometry.


[Phys. Rev. Fluids 3, 074302] Published Wed Jul 11, 2018

Sinuous distortion of vortex surfaces in the lateral growth of turbulent spots

Physical Review Fluids - Wed, 07/11/2018 - 11:00

Author(s): Yaomin Zhao, Shiying Xiong, Yue Yang, and Shiyi Chen

There is a continued debate about the generation mechanism of turbulent spots in boundary-layer transition. We use the vortex-surface field to show that the sinuous distortion of vortex surfaces plays an important role in the rapid lateral growth of turbulent spots.


[Phys. Rev. Fluids 3, 074701] Published Wed Jul 11, 2018

Non-intermittent turbulence: Lagrangian chaos and irreversibility

Physical Review Fluids - Tue, 07/10/2018 - 11:00

Author(s): Samriddhi Sankar Ray

Simulations of Lagrangian turbulence with Fourier components removed (decimation) show no effect on the level of chaos but an emergent time reversality as indicated by the ratio of Lyapunov exponents shown in the figure.


[Phys. Rev. Fluids 3, 072601(R)] Published Tue Jul 10, 2018

External intermittency compensation of dissipation scale distributions in a turbulent boundary layer

Physical Review Fluids - Tue, 07/10/2018 - 11:00

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

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