中等欠膨胀和过膨胀火箭喷焰电磁特性计算

建立了一种近 远场分区耦合计算方法来计算中等欠膨胀和过膨胀火箭喷焰的微波衰减特性 .首先在近场 ,用时间相关法求解轴对称N S方程 ,湍流模型为k ε二方程模型 ,获得近场压力参数分布 .然后求解轴对称抛物化N S方程并耦合有限速率化学动力学模型在已知的近场压力分布基础上进行空间推进 ,在近场末端获得远场初始参数 .在远场 ,直接求解轴对称抛物化N S方程 ,认为压力变化可忽略不计 ,并考虑更复杂的化学反应过程 .最后在整个流场上利用电子导电模型计算喷焰的电磁特性参数 .对中等欠膨胀和过膨胀喷焰微波衰减进行了计算和分析 ,计算结果与实验结果比较一致 .这种改进的方法可用于中等非完全膨胀火箭喷焰的微波衰减特性研究 .

Computation of Electromagnetic Properties of Mildly Overexpanded and Underexpanded Rocket Exhaust Plume

An improved near-far field divided-coupled method was established to investigate the electromagnetic properties of mildly overexpanded and underexpanded rocket exhaust plumes. Firstly, axisymmetric Navier-Stokes equations incorporated with k-ε two-equation turbulence models were solved using time-dependent approach to calculate the pressure of the near filed. Secondly, parabolized axisymmetric Navier-Stokes equations incorporated with finite-rate chemical kinetics models were marching on the detailed pressure map of the near field. The termination of the near field would yield the initial line for the far field. In addition, in the far field, the spatial-marching method was directly used under the constant pressure condition, but considering more complicated chemically reacting process. Finally, the electromagnetic parameters of the whole plume were calculated with the electron-conductive model. The calculated results of the overexpanded and underexpanded rocket exhaust plume were discussed. The predicted microwave attenuation accorded with the experimental results. This improved method is feasible for calculating the microwave attenuation characteristics of mildly non-fully expanded rocket exhaust plumes.