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(Source: Physics of Fluids)
Source: Physics of Fluids - September 28, 2016 Category: Physics Source Type: research
Dynamics of multiphase turbulent plumes with hybrid buoyancy sources in stratified environments
Deepwateroil blowouts typicallygenerate multiphase hybrid plumes where the total inlet buoyancy flux is set by the combined presence of gas,oil, and heat. We numerically investigate the effects of combined sources of inlet buoyancy on turbulent plume dynamics by varying the inputs of a dispersed, slipping gas phase and a non-slipping buoyant liquid phase in thermally stratified environments. The ability of a single momentumequation, multiphasemodel to correctly reproduce characteristic plume heights is validated for both dispersed liquid phase and pure gas bubble plumes. A hybrid case, containing buoyancy contributions fro...
Source: Physics of Fluids - September 28, 2016 Category: Physics Authors: Alexandre Fabregat Tom às, Andrew C. Poje, Tamay M. Özgökmen and William K. Dewar Source Type: research
Numerical investigation of flow-induced rotary oscillation of circular cylinder with rigid splitter plate
Numerical results offluidflow over a rotationallyoscillating circular cylinder with splitter plate are presented here. Different from the previous examinations with freely rotatable assembly, thefluid and structure interactions are treated as a coupled dynamic system by fully considering the structural inertia, stiffness, and damping. The hydrodynamic characteristics are examined in terms of reduced velocity Ur at a relatively lowReynolds number Re = 100 for different plate lengths ofL/D = 0.5, 1.0, and 1.5, where Ur =U/(Dfn), Re =UD/υ andfn = (κ/J)0.5/2 π withU the free stream velocity,D the diameter of the circular cy...
Source: Physics of Fluids - September 28, 2016 Category: Physics Authors: Lin Lu, Xiao-ling Guo, Guo-qiang Tang, Ming-ming Liu, Chuan-qi Chen and Zhi-hua Xie Source Type: research
Near-body vorticity dynamics of a square cylinder subjected to an inline pulsatile free stream flow
In the present work, the effect of an inflow sinusoidal excitation that is superimposed over the mean flow on the vortex-shedding characteristics of a square cylinder is studied. The frequency of pulsation is varied around the natural vortex-shedding frequency, and the amplitude of pulsation is varied moderately in comparison to the cylinder diameter, at a fixedReynolds number (=100). A flow regime map is prepared and compared with the experimental results, which are available for a circular cylinder that is subjected to inline excitation. We correlate the spectra to the corresponding flow regime.Visualization of the vorti...
Source: Physics of Fluids - September 28, 2016 Category: Physics Authors: Hrisheekesh Krishnan, Amit Agrawal, Atul Sharma and John Sheridan Source Type: research
Attenuation of strong external blast by foam barriers
The mitigation of externally generated strongblast waves by an aqueousfoam barrier of varying configurations within fixed distance between theexplosion origin and the object to be protected is investigated and quantified both experimentally and numerically. Theblast waves of shockMach number 4.8 at 190 mm from theexplosion plane are generated usingexploding wire technique. The initially cylindricalblast waves are transformed into a planeblast wave in a specially constructed test unit in which the experiments are performed. The shock waves emanating from thefoam barrier are captured using shadowgraph technique. A simple num...
Source: Physics of Fluids - September 27, 2016 Category: Physics Authors: S. Sembian, M. Liverts and N. Apazidis Source Type: research
Light-induced phenomena in one-component gas: The transport phenomena
The article presents thetheory of transport processes in a one-component gas located in the capillary under the action ofresonant laserradiation and the temperature and pressure gradients. The expressions for the kinetic coefficients determining heat and mass transport in the gas are obtained on the basis of the modified Boltzmann equations for the excited and unexcited particles. The Onsager reciprocal relations for cross kinetic coefficients are proven for all Knudsen numbers and for any law interaction of gas particles with each other and boundarysurface. Light-induced phenomena associated with the possible non-equilibr...
Source: Physics of Fluids - September 27, 2016 Category: Physics Authors: I. V. Chermyaninov and V. G. Chernyak Source Type: research
An experimental investigation of the supersonic turbulent boundary layer subjected to concave curvature
By employing particleimagevelocimetry, the response of aMach 2.95turbulent boundary layer to the concave curvature is experimentally investigated. The radius of the concave wall is 350 mm, and the turning angle is 20∘. Logarithmic law is well preserved in the profile of streamwise velocity at all streamwise positions despite the impact of curvature. The varying trend of principal strain rate is found to be different at different heights within the boundary layer, which cannot be explained by the suggestion given by former researchers. Based on the three-layer model proposed in this paper, distribution of the principal st...
Source: Physics of Fluids - September 26, 2016 Category: Physics Authors: Qian-cheng Wang, Zhen-guo Wang and Yu-xin Zhao Source Type: research
A simulation of gas flow: The dependence of the tangential momentum accommodation coefficient on molecular mass
The tangential momentum accommodation coefficient (TMAC) influences the rate of pressure drivenflow of a gas in a channel. The manner in which TMAC depends on the molecular mass is of importance as it influences the extent to which gasflow rates are affected by their mass, but there are conflicting opinions in the literature concerning the extent and even the sign of this dependence. We simulate theflow of the noble gases He, Ne, Ar, Kr, and Xe usingmolecular dynamics with Lennard-Jones potentials. Theinteraction with the wall is made realistic by simulating five layers of mobile atoms and allowing for adsorbed gas on the ...
Source: Physics of Fluids - September 23, 2016 Category: Physics Authors: William W. Lim, Gregg J. Suaning and David R. McKenzie Source Type: research
Non-linear interactions in a boundary layer developing over an array of cubes using stochastic estimation
In the present work, a boundary layer developing over a rough-wall consisting of staggered cubes with a plan area packing density,λp = 25%, is studied within awind tunnel using combined particle imagevelocimetry and hot-wire anemometry to investigate the non-linear interactions between large-scale momentum regions and small-scale structures induced by the presence of the roughness. Due to the highlyturbulent nature of the roughness sub-layer andmeasurement equipment limitations, temporally resolved flow measurements are not feasible, making the conventional filtering methods used for triple decomposition unsuitable for th...
Source: Physics of Fluids - September 23, 2016 Category: Physics Authors: Karin Blackman and Laurent Perret Source Type: research
Generation of a mean flow by an internal wave
We experimentally study the generation of a meanflow by a two-dimensional progressive internal gravity wave. Due to theviscous damping of thewave, a non-vanishing Reynolds stress gradient forces a meanflow. When the forcing amplitude is low, thewave amplitude is proportional to the forcing and the meanflow is quadratic in the forcing. When the forcing amplitude is large, the meanflow decreases thewave amplitude. This feedback saturates both thewave and the meanflow. The profiles of the meanflow and thewave are compared with a one-dimensional analyticalmodel. Decreasing the forcing frequency leads to awave and a meanflow lo...
Source: Physics of Fluids - September 22, 2016 Category: Physics Authors: B. Semin, G. Facchini, F. P étrélis and S. Fauve Source Type: research
Turbulence-flame interactions in DNS of a laboratory high Karlovitz premixed turbulent jet flame
In the present work, direct numerical simulation (DNS) of a laboratory premixedturbulent jetflame was performed to studyturbulence-flame interactions. Theturbulentflame features moderate Reynolds number and high Karlovitz number (Ka). The orientations of theflame normal vectorn, the vorticity vectorω and the principal strain rateeigenvectorsei are examined. The in-plane and out-of-plane angles are introduced to quantify the vector orientations, which also measure theflame geometry and the vortical structures. A general observation is that the distributions of these angles are more isotropic downstream as theflame and the ...
Source: Physics of Fluids - September 21, 2016 Category: Physics Authors: Haiou Wang, Evatt R. Hawkes and Jacqueline H. Chen Source Type: research
Expanding Taylor bubble under constant heat flux
Modelization of non-isothermal bubbles expanding in a capillary, as a contribution to the understanding of the physical phenomena taking place in Pulsating Heat Pipes (PHPs), is the scope of this paper. Theliquid film problem is simplified and solved, while the thermal problem takes into account a constant heat flux density applied at the capillary tube wall, exchanging with theliquid film surrounding the bubble and also with the capillary tube outside medium. Theliquid slugdynamics is solved using the Lucas-Washburn equation. Mass and energy balance on the vapor phase allow governing equations of bubble expansion to be wr...
Source: Physics of Fluids - September 21, 2016 Category: Physics Authors: Antoine Voirand, Adel M. Benselama, Vincent Ayel and Yves Bertin Source Type: research
Linear stability of buoyant convection in a horizontal layer of an electrically conducting fluid in moderate and high vertical magnetic field
Linear stability of buoyant convectiveflow in a horizontal layer of an electricallyconductingfluid is considered with reference to horizontal Bridgmansemiconductor crystal growth. Thefluid flows owing to the horizontal temperature gradient in the presence of a verticalmagnetic field. The main interest here is in the stability of theflow for a sufficiently strongmagnetic field, for the Hartmann numberHa> 10, and increasing to high values, of the order of 103–104. The Prandtl number,Pr, has been fixed atPr = 0.015. It is shown that besides the Hartmann number theinstability strongly depends on the type of the thermalbounda...
Source: Physics of Fluids - September 21, 2016 Category: Physics Authors: A. Hudoba, S. Molokov, S. Aleksandrova and A. Pedcenko Source Type: research
Leading edge reflection patterns for cylindrical converging shock waves over convex obstacles
The unsteady reflection of cylindrical converging shock waves over convex obstacles is investigated numerically. At the leading edge, numerical simulations show the occurrence of all types of regular and irregular reflections predicted by the pseudo-steadytheory for planar shock-wave reflections over planar surfaces, although for different combinations of wedge angles and incident shockMach number. The domain of occurrence of each reflection type and its evolution in time due to shock acceleration and to the non-planar geometry is determined and it is compared to the results of the pseudo-steadytheory. The dependence of th...
Source: Physics of Fluids - September 21, 2016 Category: Physics Authors: F. Vignati and A. Guardone Source Type: research
Nonlinear effects on electrophoresis of a charged dielectric nanoparticle in a charged hydrogel medium
The impact of the solidpolarization of a chargeddielectric particle ingelelectrophoresis is studied without imposing a weak-field or a thin Debye length assumption. The electricpolarization of adielectric particle due to an externalelectric field creates a non-uniformsurface charge density, which in turn creates a non-uniform Debye layer at the solid-gel interface. The solidpolarization of the particle, thepolarization of thedouble layer, and theelectro-osmosis of mobile ions within thehydrogel medium create a nonlinear effect on theelectrophoresis. We have incorporated those nonlinear effects by considering the electrokin...
Source: Physics of Fluids - September 20, 2016 Category: Physics Authors: S. Bhattacharyya and Simanta De Source Type: research
