稀薄滑移流区超高速非矩形防热瓦缝隙流动结构和热环境的数值模拟

Numerical simulation for the hypersonic flow structure and thermal environment of non-rectangular cavities in the rarefied slip regime

为了量化高超声速飞行器表面防热瓦缝隙的局部压力和热载荷,采用直接模拟Monte Carlo(direct simulation Monte Carlo,DSMC)方法模拟了稀薄滑移流区的防热瓦缝隙流动,考虑3类缝隙外形,即标准矩形缝隙、前部较浅缝隙和后部较浅缝隙,获得缝隙底部形状变化对缝隙内部流动特征、缝隙表面压力和热环境的影响规律。结果表明:缝隙底部形状的变化几乎不影响缝隙顶部及其附近的流场,包括流线样式、涡核位置、分离/再附处的密度分布,从而对缝隙下游侧面顶部表面压力和热流的影响也可以忽略。然而,相对于标准矩形缝隙,缝隙前部或后部变浅都会导致其底面热流变大,尤其是缝隙后部变浅甚至会使得底面的峰值热流增大近100倍。防热瓦缝隙底面一般直接就是飞行器表面,在航天器防热设计中,应特别注意这类缝隙后部较浅情况下的底面压力和热载荷。

In order to quantify the local high pressure and heat loads due to cavities or imperfections on the surface of hypersonic vehicles,the direct simulation Monte Carlo(DSMC)was utilized to simulate the rarefied hypersonic flows over cavities in the slip regime.Three kinds of cavities were taken into account:the standard rectangular cavity,the shallower-front cavity,and the shallower-back cavity,for the purpose of gaining the effects of cavity-floor shape on flow characteristics inside the cavity,surface pressure and heat transfer to the cavity surfaces.Results showed that the cavity-floor shape had little influence on flow characteristics,including the streamline pattern,vortex-core position and density distribution,inside the upper part of cavities.Therefore,the surface pressure and heat transfer to the upper part of the aft wall of the cavity was kept unchanged when the front or back part of the cavity floor became shallower.However,in comparison with the standard rectangular cavity,both the shallower-front and shallower-back cavities suffered more severe heat loads on the cavity floor.Especially,the peak value of heat transfer to the cavity floor in the case of shallower-back cavity was 100 times larger than the corresponding value in the standard rectangular cavity.In the design of spacecraft,the cavity floor is exactly taken as the spacecraft surface,so much attention should be paid to the pressure and heat loads on the cavity floor in case of shallower-back cavity.