DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number

Pradhan, S (2017) DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number. In: 53rd AIAA/SAE/ASEE Joint Propulsion Conference, 2017, 10-12 July 2017, Atlanta; Georgia.

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Abstract

The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf/\sqrtkBTvinf/m) in the range 3 < Ma < 10, and at Reynolds number number Re = (LT Uinf pinf)/μinf equal to 10 using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations to understand the flow phenomena of the leading-edge flat plate boundary layer at high Mach number 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Here, LT is the characteristic dimension, Uinf and Tinf are the free stream velocity and temperature, pinf is the free stream gas density, m is the molecular mass, μinf is the molecular viscosity based on the free stream temperature Tinf, and kB is the Boltzmann constant. The variation of stream wise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the stream wise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the stream wise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip ((Pradhan and Kumaran, J. Fluid Mech-2011); (Kumaran and Pradhan, J. Fluid Mech-2014)) at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the stream wise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain. The subsonic region near the wall, expected when a no-slip boundary condition is applied, is not present when there is wall slip at sufficiently high Mach number. In a compressible leading-edge flat plate boundary layer flows we determine the mean free path at different stream wise direction (x = 0.2, and 0.8 m) away from the plate surface, and found significant dependence on the stream wise location. This is due to the variation in the local temperature along the stream wise direction across the boundary layer by the viscous heating. The leading edge shock wave is evidently captured in the present DSMC simulations. An important finding is that the wall heating (by increasing the wall temperature in the simulations) increases the local mean free path at the wall. However away from the wall the mean free path profiles remains unaffected by the wall heating. stream wise, and wall-normal directions respectively. The velocity components in the stream wise & wall-normal directions, density, pressure and temperature are denoted by u, v, ?, p, and T respectively. The free-stream gas density is denoted by pinf, while the free-stream gas velocity and temperature are Uinf and Tinf respectively.

Item Type:	Conference Paper
Publication:	53rd AIAA/SAE/ASEE Joint Propulsion Conference, 2017
Publisher:	American Institute of Aeronautics and Astronautics Inc, AIAA
Additional Information:	cited By 0; Conference of 53rd AIAA/SAE/ASEE Joint Propulsion Conference, 2017 ; Conference Date: 10 July 2017 Through 12 July 2017; Conference Code:195549
Keywords:	Aerodynamics; Boundary layer flow; Boundary layers; Buoyancy; Density of gases; Incompressible flow; Monte Carlo methods; Propulsion; Reynolds number; Shock waves; Velocity, Direct simulation Monte Carlo; Flat plate boundary layers; No-slip boundary conditions; Pressure and temperature; Stream-wise velocities; Streamwise directions; Two Dimensional (2 D); Wall-normal direction, Mach number
Department/Centre:	Division of Mechanical Sciences > Chemical Engineering
Date Deposited:	19 Nov 2020 06:43
Last Modified:	19 Nov 2020 06:43
URI:	http://eprints.iisc.ac.in/id/eprint/66284

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