POF: Letters and Brief Communications http://scitation.aip.org/ POF: Letters and Brief Communications Spectrum of a passive scalar in moderate Reynolds number homogeneous isotropic turbulence http://link.aip.org/link/?PHF/21/111702/1&agg=rss L. Danaila and R. A. Antonia<br/> For moderate Reynolds numbers, the spectral scaling exponents of both velocity [E(k)[proportional]k] and the transported passive scalar [E(k)[proportional]k] fields exhibit departures from the asymptotic prediction m=m=5/3. However, at the same Reynolds number, the passive scalar spectrum for homoge ... [Phys. Fluids 21, 111702 (2009)] published Mon Nov 16, 2009. Localized edge states in plane Couette flow http://link.aip.org/link/?PHF/21/111701/1&agg=rss Yohann Duguet, Philipp Schlatter, and Dan S. Henningson<br/> The dynamics at the threshold of transition in plane Couette flow is investigated numerically in a large spatial domain for a certain type of localized initial perturbation, for Re between 350 and 1000. The corresponding edge state is an unsteady spotlike structure, localized in both streamwise and ... [Phys. Fluids 21, 111701 (2009)] published Fri Nov 13, 2009. Chaos in a cylinder wake due to forcing at the Strouhal frequency http://link.aip.org/link/?PHF/21/101705/1&agg=rss Paris G. Perdikaris, Lambros Kaiktsis, and George S. Triantafyllou<br/> In this letter we show that a cylinder oscillating harmonically in line with an incoming flow at a frequency equal to the natural frequency of vortex shedding induces for certain amplitudes of oscillation a chaotic state in the flow, characterized by an aperiodic lift force. The result is obtained t ... [Phys. Fluids 21, 101705 (2009)] published Thu Oct 29, 2009. Response modes of a flexible filament in the wake of a cylinder in a flowing soap film http://link.aip.org/link/?PHF/21/101704/1&agg=rss Lai-Bing Jia and Xie-Zhen Yin<br/> Flow induced vibrations are observed in many engineering applications. A flexible body located in the wake of an obstacle is usually forced to vibrate by the periodic vortices shedding from the obstacle. Here we focus on the response of the flexible body in the wake. Soap film tunnels are used to pr ... [Phys. Fluids 21, 101704 (2009)] published Thu Oct 29, 2009. Exact and asymptotic conditions on traveling wave solutions of the NavierStokes equations http://link.aip.org/link/?PHF/21/101703/1&agg=rss Y. Charles Li and Divakar Viswanath<br/> We derive necessary conditions that traveling wave and other solutions of the NavierStokes equations must satisfy in the pipe, Couette, and channel flow geometries. Some conditions are exact and must hold for any traveling wave solution or periodic solution irrespective of the Reynolds number (Re). ... [Phys. Fluids 21, 101703 (2009)] published Mon Oct 12, 2009. Tube geometry can force switchlike transitions in the behavior of propagating bubbles http://link.aip.org/link/?PHF/21/101702/1&agg=rss A. de Lozar, A. Heap, F. Box, A. L. Hazel, and A. Juel<br/> Microscale process engineering requires precise control of bubbles and droplets. We investigate geometry-induced control and find that a centered constriction in the cross section of rectangular tubes can lead to new families of steadily propagating bubbles, which localize in the least-constricted r ... [Phys. Fluids 21, 101702 (2009)] published Fri Oct 9, 2009. A simple wall-layer model for large eddy simulation with immersed boundary method http://link.aip.org/link/?PHF/21/101701/1&agg=rss F. Roman, V. Armenio, and J. Frohlich<br/> A wall-layer model is proposed for large eddy simulation of high Reynolds number turbulent flows in conjunction with immersed boundaries. The model is based on two main steps: the reconstruction of the velocity field at the first grid point off the immersed body and the modelization of the actual wa ... [Phys. Fluids 21, 101701 (2009)] published Wed Oct 7, 2009. Multiple-timescale asymptotic analysis of transient coating flows http://link.aip.org/link/?PHF/21/091702/1&agg=rss C. M. Groh and M. A. Kelmanson<br/> New stability results for the widely studied paradigm rotating cylinder coating flow problem are found using a novel multiple-timescale asymptotic approach that is not only fully automated within an algebraic-manipulator platform, but also more widely applicable to diverse evolution equations, parti ... [Phys. Fluids 21, 091702 (2009)] published Tue Sep 22, 2009. Non-Poisson statistics of settling spheres http://link.aip.org/link/?PHF/21/091701/1&agg=rss Laurence Bergougnoux and Elisabeth Guazzelli<br/> Direct tracking of the particle positions in a sedimenting suspension indicates that the particles are not simply randomly distributed. The initial mixing of the suspension leads to a microstructure which consists of regions devoid of particles surrounded by regions where particles have an excess of ... [Phys. Fluids 21, 091701 (2009)] published Tue Sep 22, 2009. Turbulence-induced secondary motion in a buoyancy-driven flow in a circular pipe http://link.aip.org/link/?PHF/21/081704/1&agg=rss Yannick Hallez and Jacques Magnaudet<br/> We analyze the results of a direct numerical simulation of the turbulent buoyancy-driven flow that sets in after two miscible fluids of slightly different densities have been initially superimposed in an unstable configuration in an inclined circular pipe closed at both ends. In the central region l ... [Phys. Fluids 21, 081704 (2009)] published Tue Aug 25, 2009. Coupled flutter of parallel plates http://link.aip.org/link/?PHF/21/081703/1&agg=rss Lionel Schouveiler and Christophe Eloy<br/> Experimental visualizations of the coupled flutter of an assembly of two, three, and four flexible parallel cantilevered plates immersed in an axial uniform flow are presented. Depending on the flow velocity, on the interplate distance, and on the plate length, different coupled modes are observed. ... [Phys. Fluids 21, 081703 (2009)] published Wed Aug 12, 2009. The behavior of subgrid-scale models near the turbulent/nonturbulent interface in jets http://link.aip.org/link/?PHF/21/081702/1&agg=rss Carlos B. da Silva<br/> The behavior of subgrid-scale models near the turbulent/nonturbulent interface in jets is analyzed by using direct numerical simulation and large-eddy simulation (LES). The subgrid scales of motion near this region are far from equilibrium and contain an important fraction of the total kinetic energ ... [Phys. Fluids 21, 081702 (2009)] published Mon Aug 10, 2009. Motion of a vortex ring in a simple shear flow http://link.aip.org/link/?PHF/21/081701/1&agg=rss M. Cheng, J. Lou, and T. T. Lim<br/> The motion and deformation of a vortex ring in a linear or simple shear flow have been simulated numerically by using the lattice Boltzmann method with multiple relaxation times. The study is motivated by a recent experiment [T. T. Lim, K. B. Lua, and K. Thet, Phys. Fluids 20, 051701 (2008)], which ... [Phys. Fluids 21, 081701 (2009)] published Wed Aug 5, 2009. The impact of a local perturbation on global properties of a turbulent wake http://link.aip.org/link/?PHF/21/071701/1&agg=rss Vladimir Parezanovic and Olivier Cadot<br/> Stationary perturbation techniques are used to investigate the sensitivity of the global properties of the wake behind a bluff body at moderate Re. The entire recirculation bubble is found to be a sensitive region for the global frequency selection and the quality of the synchronization. A striking ... [Phys. Fluids 21, 071701 (2009)] published Fri Jul 24, 2009. Experimental evidence of the kinematic Cosserat effect in dense granular flows http://link.aip.org/link/?PHF/21/051703/1&agg=rss K. S. Ananda, Jaysree Patra, and Prabhu R. Nott<br/> To capture shear localization in the flow of dense granular materials in a continuum description, it has earlier been proposed that granular materials be treated as Cosserat, or micropolar, continua. Here, we provide experimental verification of the kinematic Cosserat effect, or the deviation of the ... [Phys. Fluids 21, 051703 (2009)] published Wed May 27, 2009. Turbulent boundary layers up to Re=2500 studied through simulation and experiment http://link.aip.org/link/?PHF/21/051702/1&agg=rss P. Schlatter, R. Orlu, Q. Li, G. Brethouwer, J. H. M. Fransson et al.<br/> Direct numerical simulations (DNSs) and experiments of a spatially developing zero-pressure-gradient turbulent boundary layer are presented up to Reynolds number Re=2500, based on momentum thickness theta and free-stream velocity. For the first time direct comparisons of DNS and experiments of turbu ... [Phys. Fluids 21, 051702 (2009)] published Wed May 20, 2009. Flow behind a cylinder forced by a combination of oscillatory translational and rotational motions http://link.aip.org/link/?PHF/21/051701/1&agg=rss M. Nazarinia, D. Lo Jacono, M. C. Thompson, and J. Sheridan<br/> The flow behind a cylinder undergoing forced combined oscillatory motion has been studied. The motion consists of two independent oscillations: cross-stream translation and rotation. Previous studies have extensively investigated the effect of these motions individually on cylinder wakes; however, t ... [Phys. Fluids 21, 051701 (2009)] published Wed May 20, 2009. On the unsteady behavior of turbulence models http://link.aip.org/link/?PHF/21/041701/1&agg=rss R. Rubinstein and W. J. T. Bos<br/> Periodically forced turbulence is used as a test case to evaluate the predictions of two-equation and multiple-scale turbulence models in unsteady flows. The limitations of the two-equation model are shown to originate in the basic assumption of spectral equilibrium. A multiple-scale model based on ... [Phys. Fluids 21, 041701 (2009)] published Wed Apr 22, 2009. Maximization of granular outflow by oblique exits and by obstacles http://link.aip.org/link/?PHF/21/031701/1&agg=rss Bjorn Zelinski, Eric Goles, and Mario Markus<br/> We investigate experimentally the intermittent discharge of a granular medium out of an exit at the bottom of a vertically shaken box. Changing the orientation of the bottom shows that there exists an angle (around 20 degrees 25 degrees with respect to the horizontal) at which the mean discharge ra ... [Phys. Fluids 21, 031701 (2009)] published Fri Mar 20, 2009. Topological chaos and mixing in a three-dimensional channel flow http://link.aip.org/link/?PHF/21/021701/1&agg=rss Jie Chen and Mark A. Stremler<br/> Passive mixing is investigated in a mathematical model of steady, three-dimensional, laminar flow through a rectangular channel. Efficient stirring is achieved by imposing spatially periodic transverse boundary velocities that generate asymmetric, counter-rotating rolls aligned with the channel axis ... [Phys. Fluids 21, 021701 (2009)] published Fri Feb 13, 2009. Computational confirmation of an abnormal Mach reflection wave configuration http://link.aip.org/link/?PHF/21/011702/1&agg=rss Z. M. Hu, C. Wang, Y. Zhang, and R. S. Myong<br/> For the Mach reflection (MR) of symmetric shock waves of opposite families, only the wave configuration of an overall Mach reflection (oMR) consisting of two direct Mach reflections (DiMR+DiMR) is theoretically admissible. For asymmetric shock waves, an oMR composed of a DiMR and an inverse Mach ref ... [Phys. Fluids 21, 011702 (2009)] published Thu Jan 29, 2009.