Nonlinear dynamics of a thin liquid film deposited on a laterally oscillating corrugated surface in the high-frequency limit
The nonlinear dynamics of thinliquid films deposited on various periodically corrugated substrates, both left-right symmetric and asymmetric, subjected to lateral vibration in the high-frequency limit is investigated. The method used to derive the governing evolution equation is based on the long-wave approximation, multiscale time expansion, and averaging over the fast time scale. The resulting evolution equation contains theeffects of gravity, capillarity, vibration, and the substrate topology. The initial-boundary-value problem associated with this evolution equation is numerically solved and the system behavior is inve...
Source: Physics of Fluids - November 1, 2016 Category: Physics Authors: Selin Duruk and Alexander Oron Source Type: research
An ab initio study of the structure and atomic transport in bulk liquid Ag and its liquid-vapor interface
Several static and dynamicproperties of bulkliquid Ag at athermodynamic state near its triple point have been calculated by means ofab initio molecular dynamics simulations. The calculated static structure shows a very good agreement with the available experimental data. The dynamical structure reveals propagating excitations whose dispersion at long wavelengths is compatible with the experimental soundvelocity. Results are also reported for othertransport coefficients. Additional simulations have also been performed so as to study the structure of the freeliquid surface. The calculated longitudinal ionic density profile s...
Source: Physics of Fluids - October 31, 2016 Category: Physics Authors: Beatriz G. del Rio, David J. Gonz ález and Luis E. González Source Type: research
Beach vortices near circular topography
Finite-area monopolarvortices which propagate aroundtopography without change in shape are computed for circular seamounts and wells including the limiting cases of each: islands and infinitely deep wells. The time-dependent behaviour ofvortex pairs propagating toward circulartopography is also examined. Trajectories of point-vortex pairs exterior to thetopography are found and compared to trajectories ofvortex patches computed using contour dynamics. (Source: Physics of Fluids)
Source: Physics of Fluids - October 31, 2016 Category: Physics Authors: A. K. Hinds, E. R. Johnson and N. R. McDonald Source Type: research
Acoustic streaming and thermal instability of flow generated by ultrasound in a cylindrical container
A vertically orientatedultrasonic transducer contained within a closed cylindrical Pyrex tube was used to study theacoustic streamingflow within a cylindrical container. A particle-image velocimetry (PIV) system incorporating fluorescent 1.5μm seeding particles suspended in a mixture of diethyl-phthalate and ethanol, whose optical index was matched to that of Pyrex, was used to allow for undistorted PIVimaging within the Pyrex tube. Temperature on the end-wall surface and acoustic pressure within the cylinder were measured for different end-wall materials. Variables considered included acoustic absorption and reflection c...
Source: Physics of Fluids - October 31, 2016 Category: Physics Authors: Adam Green, Jeffrey S. Marshall, Dong Ma and Junru Wu Source Type: research
Numerical vs experimental pressure drops for Boger fluids in sharp-corner contraction flow
This paper addresses the problem of matching experimental findings with numerical prediction for the extreme experimental levels of pressure-drops observed in the 4:1 sharp-corner contractionflows, as reported by Nigen and Walters [ “Viscoelastic contractionflows: Comparison of axisymmetric and planar configurations, ” J. Non- Newtonian Fluid Mech.102, 343 –359 (2002)]. In this connection, we report on significant success in achievingquantitative agreement between predictions and experiments. This has been made possible by using a new swanINNFMmodel, employing an additional dissipative function. Notably, one can obse...
Source: Physics of Fluids - October 31, 2016 Category: Physics Authors: J. E. L ópez-Aguilar, H. R. Tamaddon-Jahromi, M. F. Webster and K. Walters Source Type: research
An investigation on the motion and deformation of viscoelastic drops descending in another viscoelastic media
In the present study, an investigation of the motion and shape deformation of drops is carried out in creeping flow to highlight the effect of viscoelastic properties on the problem. A perturbation method is employed to derive an analytical solution for the general case that both interior and exterior fluids are viscoelastic, both fluids obeying the Giesekus model. An experiment is also performed for the limiting case of an immiscible drop of a 0.03% (w/w) polyacrylamide in an 80:20 glycerol/water solution falling through a viscous Newtonian silicon oil (410 cP polydimethylsiloxane oil) in order to check the accuracy of th...
Source: Physics of Fluids - October 31, 2016 Category: Physics Authors: M. Davoodi and M. Norouzi Source Type: research
How do liquid fuel physical properties affect liquid jet development in atomisers?
The influence of liquid fuelproperties on atomisation remains an open question. The droplet sizes in sprays from atomisers operated with different fuels may be modified despite the small changes of the liquidproperties. This paper examines experimentally the development of a liquidjet injected from a plain orifice in order to evaluate changes in its behaviour due to modifications of the liquidproperties, which may influence the final atomisationcharacteristics. Two aviation kerosenes with similar, but not identical physicalproperties are considered, namely, standard JP8 kerosene as the reference fuel and bio-derived hydro-...
Source: Physics of Fluids - October 28, 2016 Category: Physics Authors: Georgios Charalampous and Yannis Hardalupas Source Type: research
Effects of unrelaxed stress tension on the weakly nonlinear instability
of viscoelastic sheets
The effects of unrelaxed stress tension on the instability of viscoelastic sheets
have been investigated through a weakly nonlinear temporal analysis. The surrounding
gas is inviscid, incompressible, and stationary. The Oldroyd-B model is applied to
describe the rheologic properties of the viscoelastic fluids, which is appropriate
for highly elastic “Boger fluids”; the high elasticity makes rational the assumption
of constant unrelaxed tension. The analytical expression of the second-order
amplitude and the dispersion relation have been obtained and solved numerically.
...
Source: Physics of Fluids - October 25, 2016 Category: Physics Authors: Luo Xie, Li-Jun Yang, Qing-Fei Fu and Li-Zi Qin Source Type: research
Energy distribution in shallow water ship wakes from a spectral analysis of the wave field
This work presents an experimental study of the effects of finite water depth on thewaves generated by aship in a towing tank. The wakes of two hull forms representative of maritime andriverships are measured for both deep water and shallow water configurations and for several Froude numbers. Thefree surface deformations are measured with an optical stereo-correlation measurement method to access a full and detailed reconstruction of thewave fields. Thespatial resolution of the reconstructed wakes allows us to perform aspectralanalysis of thewaves generated by theships and to decompose them into a near-field hydrodynamic r...
Source: Physics of Fluids - October 24, 2016 Category: Physics Authors: Cl ément Caplier, Germain Rousseaux, Damien Calluaud and Laurent David Source Type: research
Turbulence statistics downstream of a vorticity generator at low Reynolds numbers
Vortex generators (VGs) are inserted inturbulent pipe flows in order to improve mixing and heat and mass transfer while a moderate pressure drop is maintained. The purpose of the present study is to contribute to the elaboration of scaling laws for theturbulence decay downstream a row of VGs. This knowledge will help in the design of such systems, especially for optimal geometry and spacing of the VG. The experimental study is carried out usinglaser Doppler anemometry at different locations downstream of the row of VGs so as to probe the streamwise velocity field. The Taylor microscaleReynolds number Reλ ranges between 15...
Source: Physics of Fluids - October 24, 2016 Category: Physics Authors: Charbel Habchi, Thierry Lemenand, Dominique Della Valle and Hassan Peerhossaini Source Type: research
Buoyant miscible displacement flows in vertical pipe
We report on the stabilizing effect of the imposedflow and uncover the existence of two mainflow regimes at long times: a stable displacementflow and an unstable displacementflow. The transition between the two regimes occurs at a critical modified Reynolds numberRetCritical, as a function ofFr. We study in depth the stableflow regime: First, alubrication model combined with a simple initialacceleration formulation delivers a reasonable prediction to the time-dependent penetrating displacing front velocity. Second, we find two sub-regimes for stable displacements, namely, sustained-back-flows and no-sustained-back-flows. T...
Source: Physics of Fluids - October 24, 2016 Category: Physics Authors: A. Amiri, F. Larachi and S. M. Taghavi Source Type: research
Simulation of drag reduction in superhydrophobic microchannels based on parabolic gas-liquid interfaces
Based on the given parabolicgas-liquid interfaces, a two-dimensional fluidflow insuperhydrophobic microchannels is numerically simulated with the steady volume of fluid model in the laminar regime. The influence of several crucial parameters ondrag reduction effect is discussed. The results indicate that thesuperhydrophobic microchannel containing rectangularcavities displays significantdrag reduction effect. With increasing inlet velocity, thepressure drop reduction decreases slightly. Augments in thepressure drop reduction tend to be large with the increase of thecavity fraction or the decrease of the channel height. The...
Source: Physics of Fluids - October 24, 2016 Category: Physics Authors: Chunxi Li, Shuo Zhang, Quanxi Xue and Xuemin Ye Source Type: research
Frequency-wavenumber spectrum of the free surface of shallow turbulent flows over a rough boundary
Data on the frequency-wavenumber spectra anddispersion relation of the dynamic water surface in an open channelflow are very scarce. In this work, new data on the frequency-wavenumber spectra were obtained in a rectangular laboratory flume with a rough bottom boundary, over a range of subcritical Froude numbers. These data were used to study thedispersion relation of the surface waves in such shallowturbulent waterflows. The results show a complexpattern of surface waves, with a range of scales andvelocities. When the mean surfacevelocity is faster than the minimum phasevelocity of gravity-capillary waves, the wavepattern ...
Source: Physics of Fluids - October 21, 2016 Category: Physics Authors: G. Dolcetti, K. V. Horoshenkov, A. Krynkin and S. J. Tait Source Type: research
Dynamics of nonspherical compound capsules in simple shear flow
Thedynamics of an initially ellipsoidal compound capsule in a simpleshear flow is investigated numerically using a three-dimensional front-tracking finite-difference model.Membrane bending resistance is included based on Helfrich ’s energy function besides the resistances againstshear deformation and area dilatation governed by the constitutive law of Skalaket al. In this paper, we focus specifically on how the presence of a spherical inner capsule and its size affects the characteristics and transition of various dynamical states of nonspherical compound capsules (i.e., the outer capsule). Significant differences in the...
Source: Physics of Fluids - October 20, 2016 Category: Physics Authors: Zheng Yuan Luo and Bo Feng Bai Source Type: research
Lagrangian analysis of the laminar flat plate boundary layer
Theflow properties at the leading edge of a flat plate represent a singularity to the Blasiuslaminar boundary layerequations; by applying theLagrangian approach, the leading edge velocity profiles of thelaminar boundary layer over a flat plate are studied. Experimental observations as well as the theoretical analysis show an exact Gaussian distribution curve as the original starting profile of the laminar flow. Comparisons between the Blasius solution and the Gaussian curve solution are carried out providing a new insight into the physics of the laminar flow. (Source: Physics of Fluids)
Source: Physics of Fluids - October 19, 2016 Category: Physics Authors: Mohammad Gabr Source Type: research
