临近空间高速飞行器抛罩过程的动网格方法对比

飞行器抛罩是一个复杂的动力学、流体力学耦合问题,涉及六自由度运动方程与N-S方程的耦合求解,其中动网格非定常计算是关键技术。针对二维临近空间高速飞行器,将耦合过程简化为匀速旋转抛罩,对比分析了光顺重构法、重叠网格法、域动分层法三种工程易行的动网格方法的仿真结果,并得到如下结论:三种方法在整流罩关闭状态下的定常流场结果一致,均能捕捉到非定常开罩过程的典型特征,得到正确的起动结果;在非定常过程中光顺重构法的分离区吞入速度慢于重叠网格法和域动分层法;重叠网格法的计算通用性最好,域动分层法的计算速度最快,光顺重构法的理论精度最高;由于光顺重构法的网格更新对于复杂模型容易失败,域动分层法只能处理运动轨迹已知的问题,三维动力学耦合计算建议采用重叠网格法;在进行整流罩的三维设计时,应考虑溢流效应以缩小整流罩前方的大分离区,降低飞行器的控制及热防护上的困难。

Comparison of Dynamic Mesh Methods for Fairing Separation Process of Near Space High Speed Aircraft

The fairing separation process is a complex problem coupling dynamics and fluid mechanics, involving the solution of the six-degree-of-freedom equations and the N-S equations. The un-steady calculation of the dynamic mesh methods is a key technique. The coupling process was simplified to the uniform rotation process for the two-dimensional near space high speed air-craft, using smoothing and remeshing method, overset method, sliding and laying method re-spectively, which are easy to implement in engineering. The simulation results of three dynamic mesh methods were compared and analyzed, and conclusions are as follows: the steady flow fields of the three methods are consistent when fairing is closed, and they can capture the typi-cal characteristics of the unsteady fairing separation process and reach the correct start conse-quence; In the unsteady process, the disappearance speed of separation region of smoothing and remeshing method is slower than overset method and the domain dynamic layering method; overset method has the best computational flexibility, sliding and laying method has the fastest calculation speed, and smoothing and remeshing method has the highest theoretical precision. Because the grid update of smoothing and remeshing method is easy to fail for complex models, and sliding and laying method can only deal with the problem of known motion path, 3D cou-pling problems suggest the overset method. In the three-dimensional design of the fairing, the overflow effect should be considered to reduce the large separation area in front of the fairing and to reduce the difficulties in the control and thermal protection of the aircraft.