Latest papers in fluid mechanics
Author(s): Jacob Page and Rich R. Kerswell
A full Koopman decomposition for the velocity field in the Burgers equation is presented by deriving explicit expressions for the Koopman modes and eigenfunctions.
[Phys. Rev. Fluids 3, 071901(R)] Published Tue Jul 24, 2018
Author(s): W. Mostert, D. I. Pullin, R. Samtaney, and V. Wheatley
Geometrical shock dynamics is used to predict that a converging cylindrical shock forms a singularity on the shock profile through nonlinear effects.
[Phys. Rev. Fluids 3, 071401(R)] Published Mon Jul 23, 2018
Author(s): M. Jalalisendi, G. Benbelkacem, and M. Porfiri
Measurements of pressure on the surface of a rigid wedge as it enters water find that, while the presence of the cylinder elicits a predictable increase in the pressure close to the keel, it is also responsible for a pressure drop in the vicinity of the pile-up.
[Phys. Rev. Fluids 3, 074801] Published Fri Jul 20, 2018
Author(s): A. L. Velikovich and J. L. Giuliani
The classic self-similar solutions of the nonstationary compressible Euler equations obtained for a blast-wave propagation (Sedov, Taylor, and von Neumann), a shock-wave implosion (Guderley, Landau, and Stanyukovich), or an impulsive loading of a planar target (von Hoerner, Häfele, and Zel’dovich) h...
[Phys. Rev. E 98, 013105] Published Thu Jul 19, 2018
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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