微型旋翼的不可压流动数值模拟

通过求解拟压缩性修正后的Euler方程成功地模拟了悬停时微型直升机旋翼的绕流。由于拟压缩项的加入,使不可压Euler方程组的类型发生了变化,相当于使方程组变成了双曲型,因此,求解可压缩流场的时间推进解法用于本文的不可压缩流场求解。计算中,网格采用O-H拓扑形式的结构网格,空间离散采用中心有限体积法,时间推进为五步Runge-Kutta方法。采用了当地时间步长、压强阻尼及隐式残值平均方法来加速收敛。应用此方法对低速条件下旋翼悬停绕流进行了数值模拟,计算结果与实验数据吻合得较好,经气动分析,证明拟压缩性方法运用于微型直升机旋翼是完全可行的。

Numerical Simulation of Incompressible Flowfield around Micro Helicopter Rotors

Pseudo compressibility method is used to calculate the hovering flowfield of a Micro-rotor in this dissertation. This method has been found to be an efficient method for obtaining a steady-state solution to the incompressible Euler equations. With introduction of pseudo compressibility,the pressure field is coupled up with the velocity field. An O-H type grid around one blade is generated. Finite volume method with central spatial discretization and Runge-Kutta time stepping scheme is used. Three types of boundary conditions occur in the codes. These are the condition on solid body,the condition across a coordinate cut and the inflow/outflow conditions in the far field. The technique of local time stepping,pressure damping and implicit residual smoothing are used to increase the convergence rate. The computational results are in good agreement with the experimental data for the lifting case. We can conclude the pseudo compressibility method is correct and reliable in simulating micro-rotor's flow.