An axisymmetric computational model of generalized hydrodynamic theory for rarefied multi-species gas flows

On the basis of the Eu’s generalized hydrodynamic (GH) theories for diatomic single species gas and monatomic multi-species gas, an axisymmetric GH computational model for multi-species gas containing monatomic and diatomic molecules is developed for the numerical simulation of hypersonic rarefied gas flows. The multi-species GH computational model includes monatomic and diatomic species of O2,N2, NO, O, N. The mass diffusion flux of the gas mixture is included in the GH constitutive relation. In addition, the physical relationship between the mass diffusion and heat fluxes is added to the evolution equation set. The multi-species GH theory includes the rotational nonequilibrium effect of diatomic molecules by introducing excess normal stress associated with the bulk viscosity.An efficient multi-species GH numerical solver for axisymmetric rarefied flows is then developed by adopting various numerical techniques, such as an adequate nonlinear equation solver for the GH constitutive relation, an accurate flux splitting scheme, multi-grid convergence acceleration and slip-wall boundary conditions. For validation, the proposed computational model is applied to hypersonic rarefied flows over a space shuttle nose, a sphere and a reentry body as well as 1D shock structure. By comparing the results of the multi-species GH model with those of the Navier–Stokes equation and the DSMC, the accuracy and physical consistency of the GH computational model are critically examined.