Rocket nozzles accelerate combustion products or high pressure gases to supersonic/hypersonic velocities. The planar nozzles have rectangular cross-sections. At low altitude, the ambient pressure is higher than the exiting jet pressure, which leads to flow separation from the nozzle wall. In planar nozzles, asymmetric flow separation can be observed at low Nozzle Pressure Ratios. Asymmetric flow separation can lead to undesirable side forces. In the present study, numerical analysis is performed on the flow through planar nozzles. Nozzle geometries with different divergence angles and different double divergence having same area ratio are considered for flow analysis. The flow analysis is performed using commercial software ANSYS Fluent. All geometries are studied with similar boundary conditions. The numerical analysis is done on two-dimensional planar models. Reynolds Averaged Navier-Stokes, and Unsteady Reynolds Averaged Navier-Stokes equations are solved with realizable k-ε model turbulence model. The divergence angle of the nozzle having the same area ratio had a significant effect on the side load. It is found that as divergence angle increases the magnitude of side load decreases and flow becomes symmetry at low Nozzle Pressure Ratios. The design Mach number of the inner nozzle and extension length of double divergent nozzle is crucial for reducing the asymmetry of the flow. Shock reflection inside the nozzle due to discontinuity could be controlled by changing the divergence angle of the nozzle. The performance of the nozzle was seen to be augmented by introducing double divergence. The side load was profoundly affected by double divergence. It was also observed that, some double divergent nozzle had adverse side load. It was observed that asymmetry, unsteadiness, and side load of the flow was completely absent at inner nozzle having design Mach number of 1.3 for the double divergent nozzle having smaller extension length.

火箭喷嘴将燃烧产物或高压气体加速到超音速/超人速。平面喷嘴具有矩形的横截面。在低海拔处，环境压力高于出口射流压力，这导致流与喷嘴壁分离。在平面喷嘴中，可以在低喷嘴压力比下观察到不对称的流分离。不对称的流动分离会导致不希望的侧向力。在本研究中，对通过平面喷嘴的流量进行了数值分析。考虑具有不同的发散角和具有相同的面积比的不同的双发散的喷嘴几何形状用于流动分析。使用商业软件ANSYS Fluent进行流量分析。在相似的边界条件下研究所有几何形状。数值分析是在二维平面模型上进行的。用可实现的k-求解雷诺平均Navier-Stokes和非稳态雷诺平均Navier-Stokes方程ε模型湍流模型。具有相同面积比的喷嘴的发散角对侧载荷有显着影响。已经发现，随着发散角的增加，侧向载荷的大小减小，并且在低喷嘴压力比下流量变得对称。内喷嘴的设计马赫数和双发散喷嘴的延伸长度对于减少流量的不对称性至关重要。通过改变喷嘴的发散角，可以控制由于不连续而引起的喷嘴内部的冲击反射。通过引入双发散可以看到喷嘴的性能得到增强。侧向载荷受到双重发散的深刻影响。还观察到，某些双发散喷嘴具有不利的侧向载荷。据观察，不对称，不稳定，