斜切反喷管流场的数值模拟

NUMERICAL SIMULATION OF SCARFED REVERSAL NOZZLE FLOWFIELD

为了在级间分离期间提供反推力，许多固体火箭发动机前端都装有一组斜切反喷管。由于反喷管的气动型面具有许多尖点，并且在超声速区有一个台阶，喷管内存在一系列激波，而且亚声速区和超声速区互相混杂。本文用时间相关法数值模拟了反喷管流场；控制方程用ＭａｏＣｏｒｍａｃｋ显格式求数值解；边界参数采用物理边界条件和从双特征线方法推导来的有效的特征方程来计算；对于固壁边界点，在不同的区域采用不同的方法对计算方程组求数值解；对超声速台阶区，采用Ｃｈａｐｍａｎ—Ｋｏｒｓｔ模型计算。计算得到的壁面压强分布与风洞吹风实验测得的压强分布一致，计算得到的等密度线分布规律与纹影照片上的密度变化规律一致。

Many solid propellant motors use a set of scarfed reversal nozzle located on the forward of motor to provide reversal thrust during the staging event.Because the gasdynamic contours of reversal nozzle are very unsmoothed and have a step in the supersonic flow region, a series of shock waves exist in the flowfield of reversal nozzle, and the subsonic flow regions are embedded in the supersonic flow region. In this paper, the inviscid axisymmetrical and two-dimensional flowfields of reversal nozzle are calculated by use of time dependent method utilizing MacCormack explicit scheme. The boundary point parameters are computed by physical boundry condition and valid bicharacteristic compatibility equations derived from bicharacteristic method.The bicharacteristic method and finite difference method are respectively employed for calculating the parameters at solid wall points in different region.The flowfield calculation in step region is complished by use of Chapman-Korst model.The pressure distribution obtained from computation is in agreement with those from wing tunnel experiment for axisymmetrical reversal nozzle, and the computational results are consistent with photos obtained from wind tunnel experiment for rectangular reversal nozzle.