说明：  安德森《计算流体力学及其应用》第九章不可压库埃特流的数值解 9.3节 数值方法：隐式克兰克—尼科尔森方法。
(Anderson the computational fluid mechanics and its application "chapter 9 do not YaKu etta flow numerical solution of section 9.3 numerical methods: implicit g frank- Nicholson method. )