| Abstract: | ![]()
Von Neumann stability theory is applied to analyze the stability of a fullycoupled implicit (FCI) scheme based on the lower-upper symmetric Gauss-Seidel (LU-SGS)method for inviscid chemical non-equilibrium flows. The FCI scheme shows excellentstability except the case of the flows involving strong recombination reactions,and can weaken or even eliminate the instability resulting from the stiffness problem,which occurs in the subsonic high-temperature region of the hypersonic flow field. Inaddition, when the full Jacobian of chemical source term is diagonalized, the stabilityof the FCI scheme relies heavily on the flow conditions. Especially in the case of hightemperature and subsonic state, the CFL number satisfying the stability is very small.Moreover, we also consider the effect of the space step, and demonstrate that the stabilityof the FCI scheme with the diagonalized Jacobian can be improved by reducingthe space step. Therefore, we propose an improved method on the grid distributionaccording to the flow conditions. Numerical tests validate sufficiently the foregoinganalyses. Based on the improved grid, the CFL number can be quickly ramped up tolarge values for convergence acceleration. |
