材料期刊网

为了分析射流放水阀内部的非定常不可压粘性流场，在一般曲线坐标系下求解了以逆变速度为参数的不可压N-S方程和压力椭圆方程。计算采用了基于隐式SMAC格式的有限差分格式。在这种格式中，非定常流场的速度是通过使用Crank-Nicholson格式，并在每一时间步处以牛顿迭代的方法得到的；而压力椭圆方程是通过使用Tschebyscheff SLOR格式并交替改变计算方向而求解。通过使用交错网格和迎风差分，诸如改进的QUICK格式，计算过程中的误差和数值不稳定能够得到有效地控制。计算结果和实验观察得到的流动图谱对比表明，二者十分吻合。

To numerically analyze the unsteady incompressibleviscous flow around a hollow-jet valve, the incompressible Navier-Stokesequations of contravariant velocities and the elliptic pressure equation ingeneral curvilinear coodinates are solved by a finite-difference method basedon the SMAC (simplified Marker and Cell) scheme. In this scheme, withapplication of the Crank-Nicholson scheme, unsteady flow is calculatediteratively by the Newton method at each time step, and the ellipticpressure equation is solved by the Tschebyscheff SLOR method withalternating the staggered grid and upstream differences, such as themodified QUICK scheme, sparious error and numerical instabilities canbe suppressed. The calculated flow patterns are in good agreement withthose obtained by high-speed photographs. The computation results showthat the flow field behind the valve needle can be divided into threeregions, that is, a main flow region, a sheer layer region and a weakvortex region. Reynolds number and a valve opening are two factors whicheffected the unsteady characteristics of the flow field.