采用NND方法计算三维喷管气流场

本文运用NND显式差分格式，计算了三维喷管气流场。气流场计算的基本方程为一般贴体坐标系下三维守恒型的欧拉方程。采用了时间分裂法和Steger-Warming矢通量分裂技术。在喷管内沿周向的每个由轴线和壁面构成的子午面上根据泊松方程生成贴体网格。本文运用三维程序计算了轴对称JPL喷管，同时与实验结果和前人采用轴对称二维程序所计算的结果做了对比。最后，本文还计算了三维矢量喷管，计算结果与现有的实验结果一致。通过轴对称JPL喷管和三维矢量喷管的计算考核，表明建立的算法和编写的计算程序是正确的。文中提出了采用子午面形式的贴体网格时奇性轴的处理方法。计算结果表明在喷管壁面处，马赫数与压强的计算结果与实验值吻合较好，而在喷管轴线处，只有当网格较密时，才能得出与实验结果接近的计算结果。

Numerical Simulation of Three Dimensional Nozzle Flows by Using NND Difference Scheme

Non-oscillatory and Non-free parameter Dissipation(NND) difference scheme was used to calculate three dimensional nozzle flows. The flow field was computed by solving the conservative Euler equations on a body fitted curvilinear coordinates. The time splitting method and Steger-Warming flux vector splitting method was utilized. The flows in Jet Propulsion Laboratory(JPL) nozzle and flows in three dimensional thrust vectoring nozzle were carried out to validate the numerical algorithm. Comparing the computational results with experimental data and other numerical results available, a good agreement was found. A simple mesh generation method was proposed to generate body fitted grid system. It shows that the computed distributions of the computed values of Mach number and pressure are identical to the experimental curves on the surface of nozzles, while finer grids are necessary for decreasing the difference between the numerical results and the experimental date along the centerline of nozzles.