流体机械粘性流场的数值模拟方法

Method to simulate the viscous flow field in hydraulic machine

流体机械内部流动的完全不可压缩假设使得流场的求解十分困难。为了有效模拟流体机械内部的粘性流场，根据流动的物理本质，将流体的实际压缩性引入控制方程，用声速方程代替可压缩流动的能量方程，发展了一种模拟流体机械内部流场的新方法。该方法将控制方程按特征值的正负号进行矢通量分裂，相应采取前差或后差格式，提高了计算的精度和稳定性。选定的计算域将一个叶片完全包容在求解域里面，避免了尾流边界条件给定的困难。计算结果表明，分离区域的压力系数基本不变，工程上将分离区内的压力视为常数，采用死水区模型是可以接受的。

It is very difficult to simulate the flow field in hydraulic machine because of the whole incompressible assumption .A new method to simulate the flow field has been developed by introducting the real compressibility into the governing equations.The sonic velocity equation is used to take place of the energy equation of compressible flow.In terms of the flux vector splitting,the Navier Stokes equation is changed into flux vector equation,and the upwind and downwind schemes are adopted separately.The calculative results show that the pressure coefficient is nearly not change in the separated zone.The “dead zone model ” which takes the pressure as a constant in separated zone is acceptable in engineering.