稀薄狀況下噴流擴張的實驗與模擬計算之研究

Abstract

本論文中，以實驗量測和數值模擬兩種方式，來觀察以氮氣氣源之衛星控制系統中的噴嘴噴流流場。在噴嘴出口和噴嘴附近的噴流，以一個可以移動及旋轉的皮托管來量則其全壓值。另以統計為基礎的直接模擬蒙地卡羅法用來模擬噴嘴內及噴嘴附近的噴流流場，而且入口條件則以計算流體力學模擬的方式取得。比較實驗量測和數值模擬的在噴嘴出口的結果，吾人發現使用動態區域切割及變時歩法的平行化直接模擬蒙地卡羅法可以準確預測在稀薄狀態下的噴流擴張流場。因此使用動態區域切割及變時歩法之平行化直接模擬蒙地卡羅法，將有效率地模擬噴流對衛星污染及衛星姿態控制影響。

In this study, experimental and numerical investigation is performed and compared for the flow of nitrogen in a nozzle used in reaction control system on satellite and in the near field of plume. Total pressure is measured, using a traversable and rotatable pitot tube, at the exit plane of the nozzle and in the near field of the plume. A stochastic particle approach, direct simulation Monte Carlo method, is used to solve the flow field inside the nozzle and in the near field of the plume, which the inflow conditions at throat are provided by using the simulation results from a CFD solver. Comparison of the experimental data and numerical results at nozzle exit shows that the parallel DSMC method using dynamic domain decomposition and variable time-step scheme can provide an accurate description of the expanding flow under rarefied condition.