潜航飞行体深水超音速气体射流的流动稳定性研究

Analysis of the Flow Instability of Supersonic Gaseous Jets for Submarine Vehicles Working in Deep Water

深水固体火箭推进系统的可靠性和稳定性决定了整个潜航飞行体的弹道精度和飞行稳定性,其工作过程为典型的水下超音速气体射流流动过程。通过建立二维平面垂直射流几何模型,采用分离涡湍流模型仿真分析了深水条件下超音速气体射流的形貌拟序特征以及流场参数的不稳定振荡特性,对水下推进系统推力振荡现象产生的基本流动机理进行了分析。结果表明:水下超音速气体射流尾流存在高频小幅振荡,同时伴随间歇大幅振荡,这种现象与气体和水湍流混合以及中心气路激波系的不稳定运动有关;中心气路激波系的不稳定运动以及失稳重建过程会导致尾部空间压强的剧烈振荡,最终造成推力的不稳定振荡。通过对推力振荡特性的分析发现:水深越深,推力振荡幅值越大、振荡频率越高;喷管出口壁面直径越大,推力振荡幅值越大、振荡频率越高。

The reliability and stability of underwater solid rocket motor propulsion system are crucial to the ballistic accuracy and flight stability of submarine vehicles. The working process of the motor is the flow process of typical supersonic gaseous jets underwater. A planar vertical two-dimensional jet geometric model is established,and the detached-eddy simulation turbulence model is used to simulate and analyze the flow field of supersonic gaseous jets in deep-water,and the oscillation characteristics of parameters in the flow field are monitored and analyzed. The underlying flow mechanism due to thrust oscillation of underwater solid rocket motor is addressed. The results show that a high-frequency oscillation occurs in the gas wake of the underwater solid rocket motor,and is accompanied by a high-amplitude intermittent oscillation. The oscillation is related to the unstable motion of shock waves along the central gas path,which leads to a sharp oscillation of pressure in the tail space,ultimately causing thrust instability. The analysis of thrust oscillation characteristics indicates that the deeper the water depth is,the larger the thrust oscillation amplitude is,and the higher the frequency is;and the larger the diameter of wall at nozzle exit is,the larger the thrust oscillation amplitude is,and the higher the frequency is.