喷管分离流流动-热-结构顺序耦合数值模拟及试验研究

Nozzle Flow Separation Fluid-Thermal-Structure Load Transfer Coupled Analysis and Test Research

针对大膨胀比喷管气流分离状态下喷管所受的复杂载荷,采用数值方法分析喷管结构。利用有限体积二阶迎风插值格式及SST涡耗散湍流模型,结合二层增强型壁面函数,求解N-S方程、热传导方程。采用流固耦合的流动与换热模型,流场与结构温度场互为边界条件交互数据,实现了流场解算与温度场解算的耦合数值分析。应用有限元方法对给定的温度场及压力载荷作用下的结构进行了瞬态静力分析,实现了流动-热-结构的顺序耦合。采用此计算模型对轴对称拉瓦尔喷管进行了数值模拟,发现在大膨胀比下喷管发生气流分离,经分离处的斜激波后气流温度梯度及压力梯度变化较大,导致该区域应力较大。为验证模型的准确性,开展了试验研究,测得的气流分离位置和计算得到的分离位置很好的符合,说明了计算方法的有效性。

A numerical study on nozzle flow separation is presented.The finite volume method,the 2 order upwind scheme,SST k-ω turbulence model and enhanced wall function are employed to solve the Navier-Stokes and heat transfer equations.In order to solve the flow field and obtain the wall temperature distributions,numerical models have been developed incorporating both solid and fluid regions.These two regions are coupled,each one provides a boundary condition for the other,and the solution of the coupled problem has been achieved.The finite element method（FEM） is used in the transient static structure analysis under both thermal load and the pressure load.The fluid-thermal-structure load transfer coupled analysis has been realized.For the purpose of investigation the numerical method,both CFD simulation and experimental test have be down on a given over-expanded rocket nozzle.The simulation result reveals that the gas in the nozzle is separated.Dramatic temperature and pressure gradients are found in the separation zone,which leads to high stress.The computed results are validated with experimental data.The calculated pressure in the nozzle compare favorably with experimental data.Pleasant agreement between the predicted flow separation location and the data lends support to the effectiveness of this method.