Physical Review Fluids
Author(s): Purba Chatterjee, Edmund M. Tang, Pankaj Karande, and Patrick T. Underhill
In many applications of synthetic motors objects are moved through environments with component mixtures. Here active colloid propulsion is experimentally probed versus solution viscosity in hydrogen peroxide solutions, and interpreted with existing diffusion reaction models of self-diffusiophoresis.
[Phys. Rev. Fluids 3, 014101] Published Mon Jan 08, 2018
<i>A priori</i> analysis of differential diffusion for model development for scale-resolving simulations
Author(s): Franziska Hunger, Felix Dietzsch, Michael Gauding, and Christian Hasse
Direct numerical simulation data of a jet with two passive scalars is compared to explicitly filtered data of the same case with regard to the influence of the turbulent/nonturbulent interface (TNTI) on differential diffusion. Filtering is found to affect differential diffusion differently at the TNTI and in the jet core.
[Phys. Rev. Fluids 3, 014601] Published Mon Jan 08, 2018
Author(s): Paul Ritter, Stefan Zammert, Baofang Song, Bruno Eckhardt, and Marc Avila
In transitional pipe flow, isolated turbulent spots carry substantial pressure and velocity fluctuations as they travel along the pipe. A model is proposed that links the propagation speed of such spots with the exact coherent solutions to their spatial localization rate.
[Phys. Rev. Fluids 3, 013901] Published Fri Jan 05, 2018
Author(s): Nicholas G. Chisholm and Aditya S. Khair
The ability of a self-propelled swimmer to displace fluid—thus inducing mixing—in terms of the drift volume is assessed. The drift volume is found to be generally large when the Reynolds number is small, while at larger Reynolds numbers, it varies widely depending on the kinematics of swimming.
[Phys. Rev. Fluids 3, 014501] Published Fri Jan 05, 2018
[Phys. Rev. Fluids 3, 010002] Published Wed Jan 03, 2018
Effects of the Mach number on the evolution of vortex-surface fields in compressible Taylor-Green flows
Author(s): Naifu Peng and Yue Yang
The vortex-surface field (VSF) is extended to investigate the vortex dynamics in compressible Taylor-Green flows at a range of Mach numbers. The compressibility effect on the process of vortex reconnection and the interaction of shocklets and vortex surfaces using VSFs is elucidated.
[Phys. Rev. Fluids 3, 013401] Published Wed Jan 03, 2018
Author(s): Jon Alm Eriksen, Renaud Toussaint, Knut Jørgen Måløy, Eirik Flekkøy, Olivier Galland, and Bjørnar Sandnes
Gravity induces parallel growth of finger structures which forms when air displaces a granular-liquid mixture. The alignment direction, which varies between horizontal and vertical, is explained by the interplay between surface tension, yield stresses, and the hydrostatic potential.
[Phys. Rev. Fluids 3, 013801] Published Wed Jan 03, 2018
Editorial: A Tale of Two Anniversaries: 125 Years of the <i>Physical Review</i> and 25 Years of <i>Physical Review E</i>
Author(s): Matthew Salter and Michael Thoennessen
[Phys. Rev. Fluids 3, 010001] Published Tue Jan 02, 2018
Author(s): Yukinori Kametani, Ayane Kotake, Koji Fukagata, and Naoko Tokugawa
Drag reduction capability of uniform blowing in supersonic turbulent boundary layers is investigated by means of direct numerical simulation of channel flows with uniform blowing on one side and suction on the other side under subsonic and supersonic conditions.
[Phys. Rev. Fluids 2, 123904] Published Fri Dec 29, 2017
Author(s): Hassan Arbabi and Igor Mezić
The Koopman mode decomposition provides a fully data-driven framework for comprehensive dynamic analysis of complex flows. For example, the evolution of Koopman eigenvalues computed from data clearly indicates the sequence of bifurcations occurring in the state space of the flow.
[Phys. Rev. Fluids 2, 124402] Published Fri Dec 29, 2017
Author(s): X. Gloerfelt and J.-C. Robinet
A method is proposed to trigger inflow turbulence while minimizing spurious noise in order to study the noise radiated directly by a turbulent boundary layer. The strategy is based on a controlled transition by entering a resonant triad of unstable modes based on an inflectional velocity profile.
[Phys. Rev. Fluids 2, 124603] Published Fri Dec 29, 2017
Author(s): Monika Nitsche
Trajectories of vortex pairs deflected by an inclined plate undergo topological discontinuities as the plate length or angle changes. In fact, the vortex winding number jumps in a self-similar fractal fashion across gaps within gaps within gaps ad infinitum, which trap the vortices.
[Phys. Rev. Fluids 2, 124702] Published Thu Dec 28, 2017
Author(s): Juan Shi and Thomas R. Powers
Swimming microorganisms commonly encounter anisotropic environments, such as a biofilm or a liquid-crystalline solution. A simple theory for a Taylor sheet in a nematic liquid crystal is used to calculate how the swimming speed depends on the angle between the swimmer and the nematic director and also on the torque that tends to align the swimmer with the director.
[Phys. Rev. Fluids 2, 123102] Published Wed Dec 27, 2017
Asymptotic analysis of the contact-line microregion for a perfectly wetting volatile liquid in a pure-vapor atmosphere
Author(s): A. Ye. Rednikov and P. Colinet
Focused on evaporation-induced contact angles, asymptotic analyses in the limits of weak and strong Kelvin effects in the framework of Wayner’s and de Gennes’ paradigms permit a unified treatment and systematization of various isolated cases encountered in the literature.
[Phys. Rev. Fluids 2, 124006] Published Wed Dec 27, 2017
Author(s): Ehud Yarom, Alon Salhov, and Eran Sharon
The width of the spectrum of the velocities is observed in inertial wave rotating turbulence to be linearly related (at small widths) to Uksin(θ), indicating nonlinear interactions with the mean flow are the main cause of the broadening of the spectrum.
[Phys. Rev. Fluids 2, 122601(R)] Published Tue Dec 26, 2017
Author(s): Lianhua Zhu, Xiaofan Yang, and Zhaoli Guo
Under rarefied conditions, gas flow can be induced by nonuniform temperatures on bounded walls. Thermally induced flow in an enclosure with nonisothermal walls is analyzed by directly solving the gas kinetic equation via a discrete velocity method with a memory-reduction technique.
[Phys. Rev. Fluids 2, 123402] Published Tue Dec 26, 2017
Author(s): J. Bertolaccini, E. Lévêque, and P.-E. Roche
A turbulent wake retains a memory of upstream disturbances which fades over a longer distance for lower viscosity. For a zero-viscosity superfluid, numerical simulations find a subtle memory effect that explains a number of contradictory experimental observations.
[Phys. Rev. Fluids 2, 123902] Published Tue Dec 26, 2017
Author(s): M. Guttag and P. M. Reis
Inspired by the axial grooves of the Saguaro cactus, active aerodynamic drag on morphable cylinders, whose topography can be tuned pneumatically, is studied. The active samples are controlled, on demand, to obtain drag coefficients that are significantly lower than for samples with fixed morphologies.
[Phys. Rev. Fluids 2, 123903] Published Tue Dec 26, 2017
Effect of Reynolds number and saturation level on gas diffusion in and out of a superhydrophobic surface
Author(s): Hangjian Ling, Joseph Katz, Matthew Fu, and Marcus Hultmark
Gas diffusion rates in and out of superhydrophobic surfaces in transitional and turbulent boundary layers are observed and measured at varying Reynolds numbers, pressures, and dissolved gas concentrations. Results show a power-law correlation between the Sherwood and friction Reynolds number.
[Phys. Rev. Fluids 2, 124005] Published Tue Dec 26, 2017
Author(s): Pietro de Anna, Bryan Quaife, George Biros, and Ruben Juanes
Fluid flow through porous media is determined by the underlying pore structure. An analytical relationship is proposed between the distribution of the width of small openings and the distribution of low fluid velocities in the medium, which control the statistics of fluid transport and mixing.
[Phys. Rev. Fluids 2, 124103] Published Fri Dec 22, 2017