The Experts below are selected from a list of 2700 Experts worldwide ranked by ideXlab platform
Mansour Masoudi - One of the best experts on this subject based on the ideXlab platform.
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Vortex motion influencing sphere heating—Reynolds Analogy revisited
International Journal of Heat and Mass Transfer, 1999Co-Authors: Mansour MasoudiAbstract:Abstract Recently, it was reported [M. Masoudi, W.A. Sirignano, Influence of an advecting vortex on the heat transfer to a liquid droplet, Int. J. Heat Mass Transfer 40 (15) (1997) 3663–3673] that when sphere heating in a uniform flow is perturbed by vortex motion, global self-similarity is observed and the resulting correlation predicts that the sphere Nusselt number fluctuations due to vortex motion scale with the vortex circulation with unity exponent: Nu ′∼Γ 0 /(2 π ) ( Nu ′=perturbation in sphere Nusselt number, Γ 0 =non-dimensionalized initial vortex circulation). It is shown here that this computational observation is also obtained using Reynolds Analogy.
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vortex motion influencing sphere heating Reynolds Analogy revisited
International Journal of Heat and Mass Transfer, 1999Co-Authors: Mansour MasoudiAbstract:Abstract Recently, it was reported [M. Masoudi, W.A. Sirignano, Influence of an advecting vortex on the heat transfer to a liquid droplet, Int. J. Heat Mass Transfer 40 (15) (1997) 3663–3673] that when sphere heating in a uniform flow is perturbed by vortex motion, global self-similarity is observed and the resulting correlation predicts that the sphere Nusselt number fluctuations due to vortex motion scale with the vortex circulation with unity exponent: Nu ′∼Γ 0 /(2 π ) ( Nu ′=perturbation in sphere Nusselt number, Γ 0 =non-dimensionalized initial vortex circulation). It is shown here that this computational observation is also obtained using Reynolds Analogy.
Jiang Fang - One of the best experts on this subject based on the ideXlab platform.
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Direct numerical simulation of supersonic turbulent boundary layer with spanwise wall oscillation
Energies, 2016Co-Authors: Weidan Ni, Catherine Le Ribault, Lipeng Lu, Jiang FangAbstract:Direct numerical simulations (DNS) of Mach = 2.9 supersonic turbulent boundary layers with spanwise wall oscillation (SWO) are conducted to investigate the turbulent heat transport mechanism and its relation with the turbulent momentum transport. The turbulent coherent structures are suppressed by SWO and the drag is reduced. Although the velocity and temperature statistics are disturbed by SWO differently, the turbulence transports of momentum and heat are simultaneously suppressed. The Reynolds Analogy and the strong Reynolds Analogy are also preserved in all the controlled flows, proving the consistent mechanisms of momentum transport and heat transport in the turbulent boundary layer with SWO. Despite the extra dissipation and heat induced by SWO, a net wall heat flux reduction can be achieved with the proper selected SWO parameters. The consistent mechanism of momentum and heat transports supports the application of turbulent drag reduction technologies to wall heat flux controls in high-speed vehicles.
Xiao Ping Chen - One of the best experts on this subject based on the ideXlab platform.
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Effects of dimensional wall temperature on velocity-temperature correlations in supersonic turbulent channel flow of thermally perfect gas
Science China-physics Mechanics & Astronomy, 2019Co-Authors: Xiao Ping Chen, Zuchao ZhuAbstract:Direct numerical simulations of temporally evolving supersonic turbulent channel flows of thermally perfect gas are conducted at Mach number 3.0 and Reynolds number 4800 for various values of the dimensional wall temperature to study the influence of the latter on the velocity-temperature correlations. The results show that in a fully developed turbulent channel flow, as the dimensional wall temperature increases, there is little change in the mean velocity, but the mean temperature decreases. The mean temperature is found to be a quadratic function of the mean velocity, the curvature of which increases with increasing dimensional wall temperature. The concept of “recovery enthalpy” provides a connection between the mean velocity and the mean temperature, and is independent of dimensional wall temperature. The right tails of probability density function of the streamwise velocity fluctuation grows with increasing dimensional wall temperature. The dimensional wall temperature does not have a significant influence on the Reynolds Analogy factor or strong Reynolds Analogy (SRA). The modifications of SRA by Huang et al. and Zhang et al. provide reasonably good results, which are better than those of the modifications by Cebeci and Smith and by Rubesin.
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The effects of air vitiation on the supersonic turbulent channel flow using direct numerical simulation
52nd AIAA SAE ASEE Joint Propulsion Conference, 2016Co-Authors: Xiao Ping Chen, Hua-shu DouAbstract:Temporally evolving supersonic turbulent channel flows are simulated using direct numerical simulation (DNS) approach at Mach number 2.56, Reynolds number 7000 with water vapor (H2O) mass fraction from 0.00 to 0.161 to study the air vitiation effects. Then, the turbulent statistical characteristics and velocity-temperature correlations have been studied based on the DNS database. It is found that in fully developed turbulent channel flow, many of turbulent statistical characteristics used to express supersonic turbulent channel flow of pure air also hold for the H2O considered. After a nondimensional static temperature parameters introduced, the mean velocity-temperature correlation collapses between current DNS results. The results of strong Reynolds Analogy decrease with H2O mass fraction increasing, and modified strong Reynolds Analogy show a better agreement than original strong Reynolds Analogy. In addition, the correlation Ru’T’isn’t remained the same between the different H2O mass fraction cases. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.
I. I. Vigdorovich - One of the best experts on this subject based on the ideXlab platform.
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Turbulent thermal boundary layer on a plate. Reynolds Analogy and heat transfer law over the entire range of prandtl numbers
Fluid Dynamics, 2017Co-Authors: I. I. VigdorovichAbstract:Arational asymptotic theory is proposed,which describes the turbulent dynamic and thermal boundary layer on a flat plate under zero pressure gradient. The fact that the flow depends on a finite number of governing parameters makes it possible to formulate algebraic closure conditions relating the turbulent shear stress and heat flux with the gradients of the averaged velocity and temperature. As a result of constructing an exact asymptotic solution of the boundary layer equations, the known laws of the wall for velocity and temperature, the velocity and temperature defect laws, and the expressions for the skin friction coefficient, Stanton number, and Reynolds Analogy factor are obtained. The latter makes it possible to give two new formulations of the temperature defect law, one of which is identical to the velocity defect law and contains neither the Stanton number nor the turbulent Prandtl number, and the second formulation does not contain the skin friction coefficient. The heat transfer law is first obtained in the form of a universal functional relationship between three parameters: the Stanton number, the Reynolds number, and the molecular Prandtl number. The conclusions of the theory agree well with the known experimental data.
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The Reynolds Analogy and a new formulation of the temperature-defect law for a turbulent boundary layer on a plate
Doklady Physics, 2016Co-Authors: I. I. VigdorovichAbstract:A rational asymptotic theory describing the dynamic and thermal turbulent boundary layer on a plate at zero pressure gradient is proposed. The fact that the flow depends on a finite number of governing parameters makes it possible to formulate algebraic closure conditions, which relate the turbulent shear stress and heat flux to mean velocity and temperature gradients. As a result of an exact asymptotic solution of the boundary-layer equations, the known laws of the wall for the velocity and temperature and the velocity and temperature defect laws as well as the expression for the skin-friction coefficient, the Stanton number, and the Reynolds-Analogy factor are obtained. The latter implies two new formulations of the temperature-defect law, one of which is completely similar to the velocity-defect law and does not contain the Stanton number and the turbulent Prandtl number, and the other does not contain the skin-friction coefficient. A heat-transfer law that relates only thermal quantities is also obtained. The conclusions of the theory agree well with experimental data.
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The restoration coefficient and Reynolds Analogy in a boundary layer with injection and suction over the entire Prandtl number range
Fluid Dynamics, 2011Co-Authors: I. I. Vigdorovich, A. I. Leont’evAbstract:The restoration and Reynolds Analogy coefficients are calculated for a laminar self-similar boundary layer on a permeable plate over the entire possible range of variation in the Prandtl number and the injection and suction parameter.
Weidan Ni - One of the best experts on this subject based on the ideXlab platform.
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Direct numerical simulation of supersonic turbulent boundary layer with spanwise wall oscillation
Energies, 2016Co-Authors: Weidan Ni, Catherine Le Ribault, Lipeng Lu, Jiang FangAbstract:Direct numerical simulations (DNS) of Mach = 2.9 supersonic turbulent boundary layers with spanwise wall oscillation (SWO) are conducted to investigate the turbulent heat transport mechanism and its relation with the turbulent momentum transport. The turbulent coherent structures are suppressed by SWO and the drag is reduced. Although the velocity and temperature statistics are disturbed by SWO differently, the turbulence transports of momentum and heat are simultaneously suppressed. The Reynolds Analogy and the strong Reynolds Analogy are also preserved in all the controlled flows, proving the consistent mechanisms of momentum transport and heat transport in the turbulent boundary layer with SWO. Despite the extra dissipation and heat induced by SWO, a net wall heat flux reduction can be achieved with the proper selected SWO parameters. The consistent mechanism of momentum and heat transports supports the application of turbulent drag reduction technologies to wall heat flux controls in high-speed vehicles.