The Experts below are selected from a list of 63 Experts worldwide ranked by ideXlab platform
Cameron Tropea - One of the best experts on this subject based on the ideXlab platform.
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growth and separation of a start up vortex from a Two Dimensional shear layer
Physics of Fluids, 2012Co-Authors: Pooria Sattari, David E Rival, Robert J Martinuzzi, Cameron TropeaAbstract:The evolution of an isolated line vortex generated by a starting Two-Dimensional Jet is studied experimentally using time-resolved particle image velocimetry. The vortex growth in this current configuration is not linked to any externally imposed length scales or interactions with other vortical structures or walls that could potentially influence vortex growth. A model for the early-stage vortex growth, based on the transport of circulation from the shear layer into the vortex, is proposed and found to agree well with experimental data. The model provides a scaling scheme for vortex growth using shear-layer characteristic velocity and shear-layer thickness. The vortex growth is limited through a gradual separation of the vortex from the feeding shear layer, arising from decreased shear-layer curvature. This phenomenon is linked to a competition between the shear-layer tendency to remain in the streamwise direction and the induced velocity from the vortex on the shear layer. Finally, a dimensionless number representing this competition is introduced, which in turn is able to describe the gradual separation of the vortex from the shear layer.
Hadi Ahmadi - One of the best experts on this subject based on the ideXlab platform.
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effect of intermittent and sinusoidal pulsed flows on impingement heat transfer from a concave surface
International Journal of Thermal Sciences, 2014Co-Authors: Javad Mohammadpour, Arun S. Mujumdar, Mehran Rajabizargarabadi, Hadi AhmadiAbstract:Abstract The effects of square waveform (intermittent) and sinusoidal waveform pulsation are investigated on the heat transfer rate from a slot Jet impinging to a concave surface. In this respect, a numerical analysis of turbulent flow and heat transfer in a Two-Dimensional Jet is performed using the RNG k–ɛ model. The effects of Jet Reynolds number, pulsation frequency, nozzle to target surface spacing in both types of waves and the effect of the amplitude of sinusoidal waves on distribution of the surface time-averaged local Nusselt number are studied. Results show that in the pulsed Jets, the increase of frequency in the range of 20–80 Hz and the Reynolds number in the range of 4740–7200 cause the increase of the time-averaged Nusselt number compared to steady Jet cases. In the pulsed Jets, reducing the nozzle-to-surface distance causes the increase of heat transfer from the target surface. Moreover, the increase of pulse amplitude from 0.2 to 1.0 in the sinusoidal waves increases the time-averaged Nusselt number. Finally, the comparison of results indicates a considerable increase of the heat transfer rate for the square form waves than sinusoidal waves compared to the steady state data.
Pooria Sattari - One of the best experts on this subject based on the ideXlab platform.
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growth and separation of a start up vortex from a Two Dimensional shear layer
Physics of Fluids, 2012Co-Authors: Pooria Sattari, David E Rival, Robert J Martinuzzi, Cameron TropeaAbstract:The evolution of an isolated line vortex generated by a starting Two-Dimensional Jet is studied experimentally using time-resolved particle image velocimetry. The vortex growth in this current configuration is not linked to any externally imposed length scales or interactions with other vortical structures or walls that could potentially influence vortex growth. A model for the early-stage vortex growth, based on the transport of circulation from the shear layer into the vortex, is proposed and found to agree well with experimental data. The model provides a scaling scheme for vortex growth using shear-layer characteristic velocity and shear-layer thickness. The vortex growth is limited through a gradual separation of the vortex from the feeding shear layer, arising from decreased shear-layer curvature. This phenomenon is linked to a competition between the shear-layer tendency to remain in the streamwise direction and the induced velocity from the vortex on the shear layer. Finally, a dimensionless number representing this competition is introduced, which in turn is able to describe the gradual separation of the vortex from the shear layer.
Javad Mohammadpour - One of the best experts on this subject based on the ideXlab platform.
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effect of intermittent and sinusoidal pulsed flows on impingement heat transfer from a concave surface
International Journal of Thermal Sciences, 2014Co-Authors: Javad Mohammadpour, Arun S. Mujumdar, Mehran Rajabizargarabadi, Hadi AhmadiAbstract:Abstract The effects of square waveform (intermittent) and sinusoidal waveform pulsation are investigated on the heat transfer rate from a slot Jet impinging to a concave surface. In this respect, a numerical analysis of turbulent flow and heat transfer in a Two-Dimensional Jet is performed using the RNG k–ɛ model. The effects of Jet Reynolds number, pulsation frequency, nozzle to target surface spacing in both types of waves and the effect of the amplitude of sinusoidal waves on distribution of the surface time-averaged local Nusselt number are studied. Results show that in the pulsed Jets, the increase of frequency in the range of 20–80 Hz and the Reynolds number in the range of 4740–7200 cause the increase of the time-averaged Nusselt number compared to steady Jet cases. In the pulsed Jets, reducing the nozzle-to-surface distance causes the increase of heat transfer from the target surface. Moreover, the increase of pulse amplitude from 0.2 to 1.0 in the sinusoidal waves increases the time-averaged Nusselt number. Finally, the comparison of results indicates a considerable increase of the heat transfer rate for the square form waves than sinusoidal waves compared to the steady state data.
Chunpei Cai - One of the best experts on this subject based on the ideXlab platform.
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highly rarefied Two Dimensional Jet impingement on a flat plate
Physics of Fluids, 2010Co-Authors: Khaleel Khasawneh, Hongli Liu, Chunpei CaiAbstract:In this paper, we investigate highly rarefied Jet gas flows out of a Two-Dimensional slit that impinges on a flat plate which is set vertically to the plume flow direction. The plate is assumed to be completely diffusive and the gaseous plume flow out of the slit is modeled with a Maxwellian distribution function which is characterized with known number density, nonzero exit velocity, and temperature. We present some analytical collisionless flow properties for a free plume and the impingement on the plate. The outcomes include simple results of the largest shear stress on the plate and the corresponding location. Numerical simulation results obtained with the direct simulation Monte Carlo method validate the analytical collisionless flow solutions.
