Pradhan, S (2017) DSMC simulation of high mach number TaylorCouette flow. In: 21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017, 69 March 2017, Xiamen; China.

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Abstract
The main focus of this work is to characterize the TaylorCouette flow of ideal gas between two coaxial cylinders at Mach number Ma = (Uw / \sqrtkb Tw / m) in the range 0.01 < Ma < 30, and Knudsen number Kn = (1 / (\sqrt2 π d² nd (r₂  r1))) in the range 0.001 < Kn < 10, using twodimensional (2D) direct simulation Monte Carlo (DSMC) simulations 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Here, r_1 and r_2 are the radius of inner and outer cylinder respectively, U_w is the circumferential wall velocity of the inner cylinder, T_w is the wall temperature, n_d is the number density of the gas molecules, m and d are the molecular mass and diameter, and kb is the Boltzmann constant. The cylindrical surfaces are specified as being diffusely reflecting with the thermal accommodation coefficient equal to one. In the present analysis of high Mach number compressible TaylorCouette flow using DSMC method, wall slip in the temperature and the velocities are found to be significant ((Pradhan & Kumaran, J. Fluid Mech., vol. 686, 2011, pp. 109159); (Kumaran & Pradhan, J. Fluid Mech., vol. 753, 2014, pp. 307 359)). Slip occurs because the temperature/velocity of the molecules incident on the wall could be very different from that of the wall, even though the temperature/velocity of the reflected molecules is equal to that of the wall. Due to the high surface speed of the inner cylinder, significant heating of the gas is taking place. The gas temperature increases until the heat transfer to the surface equals the work done in moving the surface. The highest temperature is obtained near the moving surface of the inner cylinder at a radius of about (1.26 r_1). In a compressible TaylorCouette flow we examine the result that the splitting of the Taylor vortices takes place proportional as (L/(r_2  r_1)). The resolution suggested by our simulation is that even though the Mach number based on the wall velocity and temperature is large, the local Mach number based on the local dissipation velocity in regions of high shear decreases due to an increase in temperature. Due to this, the ratio of the mean free path and characteristics flow scale (lambda/(r_2  r_1)) appears to taper off in the high Mach number limit. A modification of the velocity profile in the viscous rotating boundary layer near the wall, which takes into account temperature and density variations, is derived. The variation of the velocity and temperature is predicted under the assumption that the increase in temperature across the viscous rotating boundary layer is larger than the wall temperature. It is found that the scaling laws do depend on the molecular model, through the dependence of viscosity and thermal conductivity on the temperature. The predicted law, are found to be in good agreement with simulations, for two different molecular models, the hardsphere and the variable hardsphere. Â© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.
Item Type:  Conference Paper 

Publication:  21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017 
Publisher:  American Institute of Aeronautics and Astronautics Inc, AIAA 
Additional Information:  cited By 0; Conference of 21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017 ; Conference Date: 6 March 2017 Through 9 March 2017; Conference Code:190149 
Keywords:  Aerodynamics; Boundary layers; Cylinders (shapes); Density of gases; Flow control; Flow of gases; Gases; Heat transfer; Molecular modeling; Molecules; Monte Carlo methods; Shear flow; Thermal conductivity; Velocity; Vortex flow, Boltzmann constants; Cylindrical surface; Direct simulation Monte Carlo; Highest temperature; Rarefied gas flow; Taylor Couette flow; Thermal accommodation coefficient; Two Dimensional (2 D), Mach number 
Department/Centre:  Division of Mechanical Sciences > Chemical Engineering 
Date Deposited:  29 Oct 2020 09:54 
Last Modified:  29 Oct 2020 09:54 
URI:  http://eprints.iisc.ac.in/id/eprint/66019 
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