at large times: 原文: At large times, the solution approaches a steady state, where the time derivatives of the flow variables approach zero. 全文摘自John D. Anderson, JR的那本CFD: 3.4.4 Some comment : The Supersonic Blunt Body Problem Revisited ...... Recall from Fig. 3.7 that unsteady inviscid flow is governed by hyperbolic equations no matter whether the flow is locally subsonic or supersonic. This provides the following oppertunity. Starting with rather arbitrary initial conditions for the flow field in the xy plane in Fig. 30, solve the unsteady, two-dimensional inviscid flow equations, marching forward in time as sketched in Fig. 3.7. At large times, the solution approaches a steady state, where the time derivatives of the flow variables approach zero. This steady state is the desired result, and what you have when you approach this steady state is a solution for the entire flow field including both the subsonic and supersonic regions. ......