Nam Lee, Ph.D.Institute of Engineering and Technology, Thu Dau Mot University (TDMU), Vietnam
Friday, February 17, 2023, 5:00 - 6:00 PM
In Person projection JH-109
Title: Extension of the Navier–Stokes–Fourier equations in hypersonic and microscale gas flows
ABSTRACT: The non-equilibrium of a rarefied gas flow can be characterized by the Knudsen number, Kn. It is defined as the ratio of the molecular mean free path, λ, to the macroscopic characteristic length, L. Nonequilibrium gas flows are most successfully simulated through the Direct Simulation Monte-Carlo (DSMC) method; however, the computational time is much longer than when using CFD, which solves the Navier-Stokes-Fourier (NSF) equations. Nonequilibrium gas flows may be simulated by solving the NSF equations with no-slip boundary conditions in the 0.001 ≤ Kn ≤ 0.01. When the Kn is large, the non-equilibrium behavior isappreciable, and there are fewer collisions between molecules in the gas flows. The lack of collisions means the NSF equations become inappropriate in rarefiedregimes indicated by a large Knudsen number. An approach to extending the NSF equations in the 0.01 ≤ Kn ≤ 0.1 is to use the velocity slip and temperature jump boundary conditions. When Kn rises into the range 0.1 ≤ Kn ≤ 1, this is called the transition-continuum regime: the NSF equations become inappropriate because the near-equilibrium fluid assumption for flows has broken down. This talk will present the extension of the NSF equations in simulating the nonequilibrium gas flows as 1) iteratively implementing the Nonlinear Coupled Constitutive Relations in the modal Discontinuous Galerkin framework and 2) the effect of the viscous heat generation in the temperature jump condition. The simulation results of the hypersonic and microscale gas flows show good agreement with the DSMC data for Kn numbers in the transition-continuum regime.
BIO: Nam Le received his Ph.D. in Computational Hypersonic Aerodynamics from the Department of Mechanical Engineering at the University of Strathclyde, Glasgow, United Kingdom, in 2011. He is currently a researcher at the Institute of Engineering and Technology, Thu Dau Mot University (TDMU), Vietnam. His scientific interests focus on hypersonic aerodynamics, microfluidics, gas-surface interactions, and computational fluid dynamics.
