用直接解法计算外掠后台阶层流流动

Numerical Analysis of Backward Facing Step Laminar Flow by Direct Solver

求解不可压流体耦合方程的直接解法（ＣＥＬＳ算法）在许多计算问题中体现了其优越性．多重网格法在加速数值计算的收敛速度方面也表现出了其有效性．作者将ＣＥＬＳ算法在多重网格下实施，对控制方程采用指数格式和虚拟时间步法进行离散，用原始变量对外掠后台阶的层流流动进行了数值计算．结果显示，外掠后台阶层流流动中，主涡、主涡下游的底部二次涡和上部二次涡开始出现的Ｒｅ数和位置均与Ａｒｍａｌｙ等人的实验数据符合良好．表明这种结合是很有效的．

Coupled equation line solver algorithm is adopted using the simultaneous direct solution for both pressure and velocity. Multigrid technique enhances solution convergence. An example is provided for the laminar flow in a pipe with an abrupt enlargement and backward facing step. The field equations are discretized by an exponential scheme with pseudo time step. Good agreements were found with the measurements of Armaly et al and the numerical results of Stella and Guj who used a vorticity velocity formulation.