Transition and turbulence in a wall-bounded channel flow at high mach number

Pradhan, S and Kumaran, V (2017) Transition and turbulence in a wall-bounded channel flow at high mach number. In: 21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017, 6 - 9 March 2017, Xiamen.

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Abstract

The turbulence in the viscous, compressible flow in a wall bounded channel is studied at high Mach (formula presented), and Reynolds numbers Re = (ρmUmH)/μw using Direct Simulation Monte Carlo (DSMC) simulations. Here, H is the channel half-width, Um is the mean velocity, ρm is the mean density, Tw is the wall temperature, m is the molecular mass, μw is the molecular viscosity based on the temperature at the isothermal wall, and kB is the Boltzmann constant. The laminar-turbulent transition is accompanied by a discontinuous change in the friction factor even at high Mach number. The transition Reynolds number increases faster than linearly with Mach number, and the Knudsen number at transition (also proportional to the ratio of Mach and Reynolds numbers) passes through a maximum as the Mach number is increased. This maximum value is small, less than 0.009, indicating that transition is a continuum phenomenon even at high Mach numbers. The transition Reynolds number predicted by the linear stability analysis is significantly higher than that observed in simulations, though its variation with Mach number is qualitatively similar. In the turbulent flow, there is slip in both the mean and fluctuating velocities at the wall; there is also significant temperature slip. These have to be incorporated in continuum DNS models to get accurate results. The variation of the ratio of the mean free path and Kolmogorov scale show the same behaviour as those in a lid-driven cavity. In the inertial sub-layer, the Van-Driest transformed velocity is found to accurately follow the logarithmic law of the wall. In the inertial sub-layer, the velocity and temperature follow the scaling proposed for the limit where the temperature increase across the sub- layer is large compared to the wall temperature.

Item Type:	Conference Paper
Publication:	21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017
Publisher:	TU Delft
Additional Information:	The copyright for this article belongs to American Institute of Aeronautics and Astronautics Inc, AIAA.
Keywords:	Aerodynamics; Linear stability analysis; Monte Carlo methods; Reynolds equation; Reynolds number; Spacecraft; Turbulence; Velocity, Boltzmann constants; Direct simulation Monte Carlo; Fluctuating velocities; Laminar turbulent transitions; Lid-driven cavities; Molecular viscosity; Temperature increase; Transition Reynolds number, Mach number
Department/Centre:	Division of Mechanical Sciences > Chemical Engineering
Date Deposited:	19 Jul 2022 04:23
Last Modified:	19 Jul 2022 04:23
URI:	https://eprints.iisc.ac.in/id/eprint/74795

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