Physics of Fluids: All Topics http://scitation.aip.org/ Physics of Fluids: All Topics The evolution of Kirchhoff elliptic vortices http://link.aip.org/link/?PHF/20/054103/1&agg=rss T. B. Mitchell and L. F. Rossi<br/> A Kirchhoff elliptic vortex is a two-dimensional elliptical region of uniform vorticity embedded in an inviscid, incompressible, and irrotational fluid. By using analytic theory and contour dynamics simulations, we describe the evolution of perturbed Kirchhoff vortices by decomposing solutions into ... [Phys. Fluids 20, 054103 (2008)] published Fri May 16, 2008. Does drop size affect the mechanism of viscoelastic drop breakup? http://link.aip.org/link/?PHF/20/053101/1&agg=rss Huaping Li and Uttandaraman Sundararaj<br/> We studied the breakup of viscoelastic drops in Newtonian liquid matrices undergoing simple shear flow. The coexistence of different breakup modes was observed. The drop size determines, to a great extent, the type of drop breakup mechanism and the critical point when the mechanism changes. Small dr ... [Phys. Fluids 20, 053101 (2008)] published Fri May 16, 2008. Onset of shear layer instability in flow past a cylinder http://link.aip.org/link/?PHF/20/054102/1&agg=rss Sanjay Mittal, Jacob J. Kottaram, and Bhaskar Kumar<br/> Global stability analysis of the flow past a cylinder is carried out to determine the critical Re for the onset of shear layer instability. To suppress the wake mode that leads to von Karman vortex shedding, flow past one-half of the cylinder is studied. The linearized perturbation equations for an ... [Phys. Fluids 20, 054102 (2008)] published Mon May 12, 2008. Effects of channel geometry on buoyancy-driven mixing http://link.aip.org/link/?PHF/20/053306/1&agg=rss Yannick Hallez and Jacques Magnaudet<br/> The evolution of the concentration and flow fields resulting from the gravitational mixing of two interpenetrating miscible fluids placed in a tilted tube or channel is studied by using direct numerical simulation. Three-dimensional (3D) geometries, including a cylindrical tube and a square channel, ... [Phys. Fluids 20, 053306 (2008)] published Mon May 12, 2008. Interface-resolved direct numerical simulation of vertical particulate channel flow in the turbulent regime http://link.aip.org/link/?PHF/20/053305/1&agg=rss Markus Uhlmann<br/> We have conducted a direct numerical simulation study of dilute turbulent particulate flow in a vertical plane channel by considering thousands of finite-size rigid particles with resolved phase interfaces. The particle diameter corresponds to approximately 11 wall units and their terminal Reynolds ... [Phys. Fluids 20, 053305 (2008)] published Fri May 9, 2008. Subcritical to supercritical mixing http://link.aip.org/link/?PHF/20/052101/1&agg=rss C. Segal and S. A. Polikhov<br/> Liquid jet injection into a quiescent gaseous environment has been experimentally and analytically studied covering subcritical to supercritical conditions. The focus was placed on the influence that the surrounding gas pressure and temperature have on the jet breakup. Under subcritical conditions, ... [Phys. Fluids 20, 052101 (2008)] published Fri May 9, 2008. Rotational dynamics of a soft filament: Wrapping transition and propulsive forces http://link.aip.org/link/?PHF/20/051703/1&agg=rss N. Coq, O. du Roure, J. Marthelot, D. Bartolo, and M. Fermigier<br/> We experimentally analyze the shape of a long elastic filament rotating in a viscous liquid. We identify a continuous but sharp transition from a straight to an helical shape, resulting from the competition between viscous stresses and elastic forces. This induced helicity generates a propulsive for ... [Phys. Fluids 20, 051703 (2008)] published Thu May 8, 2008. Discontinuity breakdown on shock wave interaction with nanosecond discharge http://link.aip.org/link/?PHF/20/056101/1&agg=rss I. A. Znamenskaya, D. A. Koroteev, and A. E. Lutsky<br/> Discontinuity breakdown conditions were experimentally realized by instant energy input in front of a plane shock wave. A shock tube and a special type of transversal nanosecond electric discharge with plasma electrodes were used for this research. A two-dimensional (2D) numerical simulation under e ... [Phys. Fluids 20, 056101 (2008)] published Wed May 7, 2008. Enhancement of mixing and adsorption in microfluidic devices by shear-induced diffusion and topography-induced secondary flow http://link.aip.org/link/?PHF/20/053304/1&agg=rss Mauricio Lopez and Michael D. Graham<br/> Continuum simulations are used to assess the effects of shear-induced diffusion and secondary flow kinematics on the enhancement of mixing and adsorption during flow of suspensions in microfluidic channels. Unidirectional flow in rectangular channels is considered, as well as flow in channels with a ... [Phys. Fluids 20, 053304 (2008)] published Wed May 7, 2008. Magnetic fluid labyrinthine instability in Hele-Shaw cell with time dependent gap http://link.aip.org/link/?PHF/20/054101/1&agg=rss A. Tatulchenkov and A. Cebers<br/> The free surface instability of a magnetic fluid in the Hele-Shaw cell with a time dependent gap is theoretically and numerically studied. The numerical algorithm is based on the boundary integral equation technique previously developed. Numerical results illustrate the role of magnetic forces in th ... [Phys. Fluids 20, 054101 (2008)] published Mon May 5, 2008. A stochastic model of coherent structures for particle deposition in turbulent flows http://link.aip.org/link/?PHF/20/053303/1&agg=rss Mathieu Guingo and Jean-Pierre Minier<br/> In this paper, we propose a new stochastic Lagrangian model that is used to compute particle deposition rate in turbulent flows. This one dimensional boundary-layer model of the velocity of the flow seen by a particle explicitly simulates the interaction of particles with the near-wall coherent phen ... [Phys. Fluids 20, 053303 (2008)] published Mon May 5, 2008. Bifurcations and symmetry breaking in the wake of axisymmetric bodies http://link.aip.org/link/?PHF/20/051702/1&agg=rss David Fabre, Franck Auguste, and Jacques Magnaudet<br/> We consider the generic problem of wake instabilities past fixed axisymmetric bodies, and focus on the extreme cases of a sphere and a flat disk. Numerical results reveal that the wakes of these two bodies evolve differently as the Reynolds number is increased. Especially, two new vortex shedding mo ... [Phys. Fluids 20, 051702 (2008)] published Mon May 5, 2008. Invariants of the velocity-gradient, rate-of-strain, and rate-of-rotation tensors across the turbulent/nonturbulent interface in jets http://link.aip.org/link/?PHF/20/055101/1&agg=rss Carlos B. da Silva and Jose C. F. Pereira<br/> The invariants of the velocity gradient (R and Q), rate-of-strain (R and Q), and rate-of-rotation (Q) tensors are analyzed across the turbulent/nonturbulent (T/NT) interface by using a direct numerical simulation (DNS) of a turbulent plane jet at Re[approximate]120. The invariants allow a detailed c ... [Phys. Fluids 20, 055101 (2008)] published Fri May 2, 2008. Does Kutta lift exist on a vortex ring in a uniform cross flow? http://link.aip.org/link/?PHF/20/051701/1&agg=rss T. T. Lim, K. B. Lua, and K. Thet<br/> Past works [Y. K. Chang and A. D. Vakili, Phys. Fluids 7, 1583 (1995); R. Sau and K. Mahesh, AIAA Paper No. 2007-1316] show that a vortex ring ejected normal to a cross flow tilts and deforms as it propagates downstream, and they attribute this phenomenon to the Kutta lift or Magnus effect. Here, we ... [Phys. Fluids 20, 051701 (2008)] published Fri May 2, 2008. Hydraulic flow through a channel contraction: Multiple steady states http://link.aip.org/link/?PHF/20/056601/1&agg=rss Benjamin Akers and Onno Bokhove<br/> We have investigated shallow water flows through a channel with a contraction by experimental and theoretical means. The horizontal channel consists of a sluice gate and an upstream channel of constant width b ending in a linear contraction of minimum width b. Experimentally, we observe upstream ste ... [Phys. Fluids 20, 056601 (2008)] published Thu May 1, 2008. Capillary threads and viscous droplets in square microchannels http://link.aip.org/link/?PHF/20/053302/1&agg=rss Thomas Cubaud and Thomas G. Mason<br/> We experimentally study the formation and evolution of threads containing more viscous liquids surrounded by less viscous, immiscible liquids through hydrodynamic focusing in square microchannels. Over a large range of viscosities and interfacial tensions, five characteristic regimes of flow behavio ... [Phys. Fluids 20, 053302 (2008)] published Thu May 1, 2008. Direct numerical simulation and analysis of instability enhancing parameters in liquid sheets at moderate Reynolds numbers http://link.aip.org/link/?PHF/20/053301/1&agg=rss Wolfgang Sander and Bernhard Weigand<br/> Direct numerical simulations based on the volume-of-fluid method have been performed in order to identify the influence of the inflow velocity conditions on the sensitivity of primary breakup phenomena. A liquid sheet ejected into a gaseous environment at moderate Reynolds numbers ranging from Re=30 ... [Phys. Fluids 20, 053301 (2008)] published Thu May 1, 2008. Inclusion of heat transfer computations for particle laden flows http://link.aip.org/link/?PHF/20/040604/1&agg=rss Zhi-Gang Feng and Efstathios E. Michaelides<br/> A newly developed direct numerical simulation method has been used to study the dynamics of nonisothermal cylindrical particles in particulate flows. The momentum and energy transfer equations are solved to compute the effects of heat transfer in the sedimentation of particles. Among the effects exa ... [Phys. Fluids 20, 040604 (2008)] published Wed Apr 30, 2008. Shape oscillations on bubbles rising in clean and in tap water http://link.aip.org/link/?PHF/20/040705/1&agg=rss Christian Veldhuis, Arie Biesheuvel, and Leen van Wijngaarden<br/> This paper deals with air bubbles rising in purified water in the range of equivalent diameters where surface oscillations appear on the interface. The shape of the bubbles including these capillary distortions is recorded by taking a large number of high speed pictures for each spiraling or zigzagg ... [Phys. Fluids 20, 040705 (2008)] published Wed Apr 30, 2008. Experimental techniques for multiphase flows http://link.aip.org/link/?PHF/20/040605/1&agg=rss Robert L. Powell<br/> This review discusses experimental techniques that provide an accurate spatial and temporal measurement of the fields used to describe multiphase systems for a wide range of concentrations, velocities, and chemical constituents. Five methods are discussed: magnetic resonance imaging (MRI), ultrasoni ... [Phys. Fluids 20, 040605 (2008)] published Wed Apr 30, 2008. Pairwise interaction of capsules in simple shear flow: Three-dimensional effects http://link.aip.org/link/?PHF/20/040801/1&agg=rss Etienne Lac and Dominique Barthes-Biesel<br/> We use a boundary integral formulation to investigate the collision of two identical capsules in simple shear flow. Each capsule consists of a viscous liquid drop enclosed by an elastic membrane. The hydrodynamic interaction is characterized by an irreversible cross-flow displacement after the capsu ... [Phys. Fluids 20, 040801 (2008)] published Wed Apr 30, 2008. Dissipation and enstrophy in isotropic turbulence: Resolution effects and scaling in direct numerical simulations http://link.aip.org/link/?PHF/20/045108/1&agg=rss D. A. Donzis, P. K. Yeung, and K. R. Sreenivasan<br/> Existing experimental and numerical data suggest that the turbulence energy dissipation and enstrophy (i.e., the square of vorticity) possess different scaling properties, while available theory suggests that there should be no differences at sufficiently high Reynolds numbers. We have performed a s ... [Phys. Fluids 20, 045108 (2008)] published Wed Apr 30, 2008. The mechanism of surfactant effects on drop coalescence http://link.aip.org/link/?PHF/20/040802/1&agg=rss Bing Dai and L. Gary Leal<br/> We utilize numerical solutions, based on a boundary-integral scheme, to investigate the mechanisms by which surfactant influences the coalescence of a pair of equal size drops that undergo a head-on collision in a biaxial linear flow. It is known that the addition of surfactant inhibits coalescence ... [Phys. Fluids 20, 040802 (2008)] published Wed Apr 30, 2008. Numerical study on the shear-induced lift force acting on a spherical bubble in aqueous surfactant solutions http://link.aip.org/link/?PHF/20/040704/1&agg=rss Masato Fukuta, Shu Takagi, and Yoichiro Matsumoto<br/> A single bubble motion in aqueous surfactant solutions is discussed in this paper. We focus on the change of the lift force acting on a bubble in a linear shear flow under the condition that the bubble surface is contaminated by surfactant adsorption which leads the Marangoni effect. With an increas ... [Phys. Fluids 20, 040704 (2008)] published Wed Apr 30, 2008. Mixing and evaporation of liquid droplets injected into an air stream flowing at all speeds http://link.aip.org/link/?PHF/20/040804/1&agg=rss F. Moukalled and M. Darwish<br/> This paper deals with the formulation, implementation, and testing of three numerical techniques based on (i) a full multiphase approach, (ii) a multisize-group (MUSIG) approach, and (iii) a heterogeneous MUSIG (H-MUSIG) approach for the prediction of mixing and evaporation of liquid droplets inject ... [Phys. Fluids 20, 040804 (2008)] published Wed Apr 30, 2008. Effect of bubble deformability in turbulent bubbly upflow in a vertical channel http://link.aip.org/link/?PHF/20/040701/1&agg=rss Jiacai Lu and Gretar Tryggvason<br/> As bubbles rising in a vertical channel with upflow become bigger, it is well known that the void fraction distribution changes in a fundamental way, from a wall peak for small bubbles to a maximum void fraction at the channel center for larger bubbles. Here, we use direct numerical simulations of b ... [Phys. Fluids 20, 040701 (2008)] published Wed Apr 30, 2008. Statistical equilibrium of bubble oscillations in dilute bubbly flows http://link.aip.org/link/?PHF/20/040902/1&agg=rss Tim Colonius, Rob Hagmeijer, Keita Ando, and Christopher E. Brennen<br/> The problem of predicting the moments of the distribution of bubble radius in bubbly flows is considered. The particular case where bubble oscillations occur due to a rapid (impulsive or step change) change in pressure is analyzed, and it is mathematically shown that in this case, inviscid bubble os ... [Phys. Fluids 20, 040902 (2008)] published Wed Apr 30, 2008. Suspension properties at finite Reynolds number from simulated shear flow http://link.aip.org/link/?PHF/20/040602/1&agg=rss Pandurang M. Kulkarni and Jeffrey F. Morris<br/> This work examines the role of particle-scale inertia in a monodisperse suspension of non-Brownian and neutrally buoyant spherical particles subjected to simple-shear flow. The dimensionless parameters governing the problem are the solid-volume fraction phi and the Reynolds number defined Re=rhogamm ... [Phys. Fluids 20, 040602 (2008)] published Wed Apr 30, 2008. Quantifying microbubble clustering in turbulent flow from single-point measurements http://link.aip.org/link/?PHF/20/040702/1&agg=rss Enrico Calzavarini, Thomas H. van den Berg, Federico Toschi, and Detlef Lohse<br/> Single-point hot-wire measurements in the bulk of a turbulent channel have been performed in order to detect and quantify the phenomenon of preferential bubble accumulation. We show that statistical analysis of the bubble-probe colliding-time series can give a robust method for investigation of clus ... [Phys. Fluids 20, 040702 (2008)] published Wed Apr 30, 2008. A weakly nonlocal anisotropic fluid model for inhomogeneous Stokesian suspensions http://link.aip.org/link/?PHF/20/040601/1&agg=rss J. D. Goddard<br/> A continuum model is proposed for a weakly inhomogeneous Stokesian suspensions, as an extension with minor amendments of a previous work on homogeneous suspensions [J. D. Goddard, J. Fluid Mech. 568, 1 (2006)]. In the present model, stress and particle flux are given as invariant tensor functions of ... [Phys. Fluids 20, 040601 (2008)] published Wed Apr 30, 2008. Interacting two-dimensional bubbles and droplets in a yield-stress fluid http://link.aip.org/link/?PHF/20/040901/1&agg=rss John P. Singh and Morton M. Denn<br/> We study the buoyancy-driven motion of two-dimensional bubbles and droplets in a Bingham fluid using a regularization method. The finite-element computations are carried out using the method of level sets to track the interface. We find that multiple bubbles and droplets can move in a body force fie ... [Phys. Fluids 20, 040901 (2008)] published Wed Apr 30, 2008. Squeezing of a periodic emulsion through a cubic lattice of spheres http://link.aip.org/link/?PHF/20/040803/1&agg=rss Alexander Z. Zinchenko and Robert H. Davis<br/> Squeezing of a periodic, highly concentrated emulsion of deformable drops through a dense, simple cubic array of solid spherical particles at zero Reynolds number is simulated by considering one drop in a periodic cell. The particles are rigidly held in space. The drops with nondeformed diameter com ... [Phys. Fluids 20, 040803 (2008)] published Wed Apr 30, 2008. Transonic flows of dense gases over finite wings http://link.aip.org/link/?PHF/20/046103/1&agg=rss P. Cinnella<br/> Transonic inviscid flows of dense gases of the BetheZel'dovichThompson (BZT) type over finite wings are numerically investigated. BZT gases are fluids of the retrograde type (i.e., that superheat when expanded), which exhibit a region of negative values of the fundamental derivative of gas dynamics ... [Phys. Fluids 20, 046103 (2008)] published Wed Apr 30, 2008. Some issues concerning large-eddy simulation of inertial particle dispersion in turbulent bounded flows http://link.aip.org/link/?PHF/20/040603/1&agg=rss C. Marchioli, M. V. Salvetti, and A. Soldati<br/> The problem of accurate EulerianLagrangian modeling of inertial particle dispersion in large-eddy simulation (LES) of turbulent wall-bounded flows is addressed. We run direct numerical simulation (DNS) of turbulent channel flow at shear Reynolds number Re=150 and corresponding a priori and a posteri ... [Phys. Fluids 20, 040603 (2008)] published Wed Apr 30, 2008. Cylindrical bubble dynamics: Exact and direct numerical simulation results http://link.aip.org/link/?PHF/20/040903/1&agg=rss Can F. Delale, Gretar Tryggvason, and Selman Nas<br/> The axially symmetric collapse and growth of a cylindrical bubble are considered. A universal law of cylindrical bubble dynamics is obtained when the pressure at the boundary and that inside the bubble satisfy certain conditions. Both vapor bubbles having constant pressure and gas bubbles obeying th ... [Phys. Fluids 20, 040903 (2008)] published Wed Apr 30, 2008. Numerical investigation of three-dimensional cloud cavitation with special emphasis on collapse induced shock dynamics http://link.aip.org/link/?PHF/20/040703/1&agg=rss Gunter H. Schnerr, Ismail H. Sezal, and Steffen J. Schmidt<br/> The aim of the present investigation is to model and analyze compressible three-dimensional (3D) cavitating liquid flows with special emphasis on the detection of shock formation and propagation. We recently developed the conservative finite volume method CATUM (Cavitation Technische Universitat Mun ... [Phys. Fluids 20, 040703 (2008)] published Wed Apr 30, 2008. The effect of soluble surfactant on the transient motion of a buoyancy-driven bubble http://link.aip.org/link/?PHF/20/040805/1&agg=rss Savas Tasoglu, Utkan Demirci, and Metin Muradoglu<br/> The effect of soluble surfactants on the unsteady motion and deformation of a bubble rising in an otherwise quiescent liquid contained in an axisymmetric tube is computationally studied by using a finite-difference/front-tracking method. The unsteady incompressible flow equations are solved fully co ... [Phys. Fluids 20, 040805 (2008)] published Wed Apr 30, 2008. Report on the IUTAM Symposium on Recent Advances in Multiphase Flows: Numerical and Experimental (11--14 June 2007, Istanbul, Turkey) http://link.aip.org/link/?PHF/20/040501/1&agg=rss Andreas Acrivos and Can F. Delale<br/> ... [Phys. Fluids 20, 040501 (2008)] published Wed Apr 30, 2008. Development of kinetic-based energy exchange models for noncontinuum, ionized hypersonic flows http://link.aip.org/link/?PHF/20/046102/1&agg=rss T. Ozawa, Jiaqiang Zhong, and D. A. Levin<br/> Ultrahigh Mach number re-entry vehicles create sufficiently energetic flow conditions with substantial ionization occurring in the noncontinuum flow regime. To model these noncontinuum, ionized, and thermochemically nonequilibrium flows, a direct simulation Monte Carlo (DSMC) approach is investigate ... [Phys. Fluids 20, 046102 (2008)] published Tue Apr 29, 2008. Thermosolutal convection in a horizontal porous layer heated from below in the presence of a horizontal through flow http://link.aip.org/link/?PHF/20/044109/1&agg=rss D. V. Lyubimov, T. P. Lyubimova, A. Mojtabi, and E. S. Sadilov<br/> In this paper, we study the effect of a homogeneous longitudinal through flow on the onset of convection in a horizontal porous layer saturated by a binary fluid and heated from below or above. The layer boundaries are subjected to a constant heat flux. The investigation is made by taking the Soret ... [Phys. Fluids 20, 044109 (2008)] published Tue Apr 29, 2008. Asymptotic regimes of ridge and rift formation in a thin viscous sheet model http://link.aip.org/link/?PHF/20/043103/1&agg=rss Carlos Alberto Perazzo and Julio Gratton<br/> We numerically and theoretically investigate the evolution of the ridges and rifts produced by the convergent and divergent motions of two substrates over which an initially uniform layer of a Newtonian liquid rests. We put particular emphasis on the various asymptotic self-similar and quasi-self-si ... [Phys. Fluids 20, 043103 (2008)] published Mon Apr 28, 2008. A priori assessment of closures for scalar dissipation rate transport in turbulent premixed flames using direct numerical simulation http://link.aip.org/link/?PHF/20/045106/1&agg=rss N. Chakraborty, J. W. Rogerson, and N. Swaminathan<br/> The scalar dissipation rate transport in both the corrugated flamelet and thin reaction zone regimes is studied using three-dimensional direct numerical simulation (DNS) databases for freely propagating statistically planar turbulent premixed flames. Both flames have comparable turbulent Reynolds nu ... [Phys. Fluids 20, 045106 (2008)] published Mon Apr 28, 2008. Control of a separating boundary layer with Lorentz force actuators http://link.aip.org/link/?PHF/20/045107/1&agg=rss Srinivasan Dattarajan and Hamid Johari<br/> The effect of time-periodic spanwise Lorentz forces on flow separation in a weakly conductive fluid is examined. An array of alternately arranged electrodes and permanent magnets constituted an electromagnetohydrodynamic actuator, which was flush mounted on a hydrofoil model with a flap that was inc ... [Phys. Fluids 20, 045107 (2008)] published Mon Apr 28, 2008. A mesoscopic rheological model of immiscible blends with the interface covered with a surface active agent http://link.aip.org/link/?PHF/20/043102/1&agg=rss Jian Feng Gu, Miroslav Grmela, and Mosto Bousmina<br/> The MaffettoneMinale mesoscopic rheological model of immiscible blends is extended to blends that include a surface active agent. Its nonuniform distribution on the interface (assumed to be the surface of droplets) and the associated with it nonuniform distribution of the surface tension and the Mar ... [Phys. Fluids 20, 043102 (2008)] published Mon Apr 28, 2008. Coalescence of Tollmien--Schlichting and interfacial modes of instability in two-fluid flows http://link.aip.org/link/?PHF/20/044108/1&agg=rss Serkan Ozgen<br/> An extensive parametric study is performed to bring out the details of the mode coalescence phenomenon in a two-fluid boundary-layer stability problem. The solution consists of numerically solving the OrrSommerfeld equation. The mode coalescence occurs between the TollmienSchlichting (TS) mode also ... [Phys. Fluids 20, 044108 (2008)] published Mon Apr 28, 2008. Effect of an electric field on film flow down a corrugated wall at zero Reynolds number http://link.aip.org/link/?PHF/20/042103/1&agg=rss D. Tseluiko, M. G. Blyth, D. T. Papageorgiou, and J.-M. Vanden-Broeck<br/> The effect of an electric field on a liquid layer flowing down an inclined, corrugated wall at zero Reynolds number is investigated. The layer is taken to be either a perfect conductor or a perfect dielectric. The region above the layer is assumed to be a perfect dielectric. Steady flow down a wall ... [Phys. Fluids 20, 042103 (2008)] published Mon Apr 28, 2008. Shear-induced particle migration in binary colloidal suspensions http://link.aip.org/link/?PHF/20/043306/1&agg=rss Denis Semwogerere and Eric R. Weeks<br/> We present experimental investigations of the spatial and temporal evolution of particle migration in pressure driven flows of Brownian particle suspensions. Binary suspensions of 1.4 and 3.0 [mu]m diameter colloidal particles are pumped through a 50 x 500 [mu]m rectangular-cross-section capillary ... [Phys. Fluids 20, 043306 (2008)] published Fri Apr 25, 2008. Large scale rotating motions in a multiple jets combustor http://link.aip.org/link/?PHF/20/041705/1&agg=rss Christophe Duwig and Ephraim Gutmark<br/> The flow dynamics of a multiple jet combustor is investigated using large eddy simulation. This particular combustor geometry is designed to mix hot combustion products from a central recirculation zone into the surrounding fuel/air jets. Using proper orthogonal decomposition, a large scale rotation ... [Phys. Fluids 20, 041705 (2008)] published Fri Apr 25, 2008. Direct numerical simulation of transitions towards structural vacillation in an air-filled, rotating, baroclinic annulus http://link.aip.org/link/?PHF/20/044107/1&agg=rss Peter L. Read, Pierre Maubert, Anthony Randriamampianina, and Wolf-Gerrit Fruh<br/> The route to chaos of baroclinic waves in a rotating, stratified fluid subjected to lateral heating can occur via several possible routes, involving either low-dimensional, quasiperiodic states or via a series of secondary small-scale instabilities. In a recent paper, we have discussed direct numeri ... [Phys. Fluids 20, 044107 (2008)] published Fri Apr 25, 2008. Kolmogorov 4/5 law, nonlocality, and sweeping decorrelation hypothesis http://link.aip.org/link/?PHF/20/041704/1&agg=rss M. Kholmyansky and A. Tsinober<br/> We report results of experiments at large Reynolds numbers, confirming the equivalent form of the Kolmogorov 4/5 law obtained recently by Hosokawa [Prog. Theor. Phys. 118, 169 (2007)]. This, as well as purely kinematic exact relations, demonstrates one of the important aspects of nonlocality of turb ... [Phys. Fluids 20, 041704 (2008)] published Fri Apr 25, 2008. On slip velocity boundary conditions for electroosmotic flow near sharp corners http://link.aip.org/link/?PHF/20/043603/1&agg=rss Thomas J. Craven, Julia M. Rees, and William B. Zimmerman<br/> The HelmholtzSmoluchowski (HS) slip velocity boundary condition is often used in computational models of microchannel flows because it allows the motion of the electric double layer (EDL) to be approximated without resolving the charge density profiles close to the walls while dramatically reducing ... [Phys. Fluids 20, 043603 (2008)] published Thu Apr 24, 2008. Open-loop control of fully nonlinear self-excited oscillations http://link.aip.org/link/?PHF/20/041703/1&agg=rss M. P. Hallberg and P. J. Strykowski<br/> Experiments conducted using a low-density axisymmetric jet reveal that the self-excited nature can be altered by modulating the external pressure field using an acoustic driver. A region exists in the forcing frequency-amplitude space where the self-sustaining frequency is entirely absent and solely ... [Phys. Fluids 20, 041703 (2008)] published Thu Apr 24, 2008. Implications of hydrophobic interactions and consequent apparent slip phenomenon on the entrance region transport of liquids through microchannels http://link.aip.org/link/?PHF/20/043602/1&agg=rss Suman Chakraborty and Kumar Dinkar Anand<br/> The implications of entrance region transport in hydrophobic microchannels are theoretically and experimentally investigated in this work. Detailed analytical solutions are derived, depicting the dependences of the liquid phase velocity profiles, entrance lengths, and friction factor variations on t ... [Phys. Fluids 20, 043602 (2008)] published Tue Apr 22, 2008. Reynolds number dependence of plane jet development in the transitional regime http://link.aip.org/link/?PHF/20/044105/1&agg=rss P. R. Suresh, K. Srinivasan, T. Sundararajan, and Sarit K. Das<br/> The transitional characteristics of plane turbulent jets have been investigated in the present study. Hot wire measurements have been performed for a jet issuing from a rectangular nozzle of aspect ratio 20, for Reynolds number varying in the range 250<=Re<=6250. In this range, the characteristics o ... [Phys. Fluids 20, 044105 (2008)] published Mon Apr 21, 2008. Stochastic synchronization of the near wall turbulence http://link.aip.org/link/?PHF/20/045105/1&agg=rss Sedat F. Tardu<br/> We investigate the characteristics of the instantaneous phases and amplitudes of the wavelet coefficients applied to the fluctuating wall shear stress and longitudinal velocity in the low buffer layer of a fully developed turbulent boundary layer. We show that the instantaneous phase exhibits long q ... [Phys. Fluids 20, 045105 (2008)] published Mon Apr 21, 2008. Effect of an axial jet on vortex merging http://link.aip.org/link/?PHF/20/047101/1&agg=rss David Marles and Ismet Gursul<br/> Experiments were conducted to understand the effect of an axial jet on the merging process of a simulated flap-edge and wing-tip corotating vortex pair in the near wake. Cross-flow velocity measurements and flow visualization were performed for the three realistic jet positions on both equal and une ... [Phys. Fluids 20, 047101 (2008)] published Mon Apr 21, 2008. Three-dimensional structure of confined swirling jets at moderately large Reynolds numbers http://link.aip.org/link/?PHF/20/044104/1&agg=rss E. Sanmiguel-Rojas, M. A. Burgos, C. del Pino, and R. Fernandez-Feria<br/> We have performed a series of three-dimensional (3D) numerical simulations of the incompressible flow discharging from a rotating pipe into a coaxial static cylindrical container through a sudden expansion. We have considered several values of the Reynolds number based on the pipe flow rate Re betwe ... [Phys. Fluids 20, 044104 (2008)] published Mon Apr 21, 2008. Transformation of premixed flame behavior with hydrodynamic and body-force instabilities http://link.aip.org/link/?PHF/20/044106/1&agg=rss Kuo-Long Pan<br/> Flame dynamics such as the formation of wrinkles is caused by instabilities such as thermal expansion and buoyancy. We have studied the combined thermal and buoyancy effects on the propagation of a premixed flame by using a front-tracking method. It was found that though wrinkled surface could be st ... [Phys. Fluids 20, 044106 (2008)] published Mon Apr 21, 2008. Velocity fluctuations and hydrodynamic diffusion in finite-Reynolds-number sedimenting suspensions http://link.aip.org/link/?PHF/20/043305/1&agg=rss Xiaolong Yin and Donald L. Koch<br/> The velocity variance and the hydrodynamic diffusivity for a finite-Reynolds-number settling suspension are determined from lattice-Boltzmann simulations of many particles in cubic cells with periodic boundary conditions. The velocity variance is found to grow logarithmically with the size of the co ... [Phys. Fluids 20, 043305 (2008)] published Mon Apr 21, 2008. Application of compact neural network for drag reduction in a turbulent channel flow at low Reynolds numbers http://link.aip.org/link/?PHF/20/045104/1&agg=rss Li Vodinh Lorang, Berengere Podvin, and Patrick Le Quere<br/> The aim of the present work is to develop neural networks for flow estimation and control in a turbulent channel flow at low Reynolds number. The control strategy considered here is the opposition strategy of Choi et al. [Active turbulence control for drag reduction in wall-bounded flows, J. Fluid M ... [Phys. Fluids 20, 045104 (2008)] published Fri Apr 18, 2008. Coalescence of two viscoelastic droplets connected by a string http://link.aip.org/link/?PHF/20/043101/1&agg=rss Jianmao Yang and Yuanze Xu<br/> A new type of coalescence of viscoelastic droplets is described and analyzed. A viscoelastic drop of polyisobutene (PIB) containing high molar mass PIB (HPIB), suspended in polydimethylsiloxane, is separated into two droplets connected by a string, which is called bead-string-bead (BSB), through rep ... [Phys. Fluids 20, 043101 (2008)] published Thu Apr 17, 2008.