再入式飞行器不同绕流状态的底部流动特征

再入式飞行器在不同雷诺数条件下会出现层流、转捩以及湍流流动状态,采用大涡模拟方法细致地刻画了类神舟返回舱外形不同绕流状态下的底部流动形态以及稳定性特征,从肩部剪切失稳、底部分离失稳、尾迹发展区以及远尾迹区的耦合失稳等多个角度分析了其底部流动特征的异同.结果表明:不同绕流状态下类神舟返回舱外形的底部流动特征存在明显差异.在低雷诺数条件下类神舟返回舱外形绕流基本为层流状态,其肩部剪切层失稳较晚,底部分离区较大,尾迹区域类卡门涡街的振荡幅值较小;在高雷诺数条件下类神舟返回舱外形绕流存在转捩和湍流行为,其肩部剪切层失稳迅速,底部分离区较小,尾迹区域类卡门涡街的振荡幅值较大;低和高雷诺数条件对肩部剪切失稳模式存在明显影响,对底部流动结构失稳模式影响较小.

Base Flow Characteristic of the Reentry Vehicle with Different Flow Stage

There are some flow stage around the reentry vehicle under different Reynolds number condition, such as laminar, transition, turbulence. Base flow characteristic of reentry vehicle under different Reynolds number condition are investigated by means of large eddy simulation (LES), base flow patterns and stability characteristics of reentry vehicle are obtained. Physical mechanisms of base flow instability are analyzed from the aspects of shoulder shear instability, base flow structure instability and wake region instability. The results show that under low Reynolds number condition flow stage around the reentry vehicle is laminar flow, shoulder shear instability is late, separation region is large, oscillation amplitude of the Karman vortex street is small; under high Reynolds number condition flow stage around the reentry vehicle is transition and turbulence, shoulder shear instability is fast, separation zone is small, oscillation amplitude of the Karman vortex street is large; different Reynolds number condition has a great influence on the shoulder shear instability mode and a small influence on base flow structure instability mode.