孔室內噴流之流場分析

Abstract

本文利用數值方法對噴射衝擊流流入一孔室內進行其暫態過程的 研究與分析。本文利用有限差分方程以可壓縮流模式解Navier-Stokes Nquations，並加入理想氣體方程及雙方程紊流模式求得流場之暫態過 程及衝擊壁面之壓力分佈。本文研究的範圍包含兩種不同大小孔室， 及四種不同噴流出口狀態做比較，並設定不同噴流出口閥的關閉時間。 結果顯示，對於較大尺寸之孔室，室內將產生渦漩，且渦漩的發生決 定衝擊壁面的壓力分佈。對於較小尺寸之孔室，衝擊壁面將呈現整體 而一致性的壓力變化。在噴流的初始及噴流出口閥截斷關閉之際，皆 將產生急劇的壓力變化，且壓力呈現振蕩不穩定現象。

The aim of the study is to investigate a jet flow which impinging into a cavity numerically. For the analysis of transient flow field and the pressure distributions on the impinging flat plate, the finite volume method with turbulence k-ε model is adopted to solve the governing equations, which include ideal-gas equation. The scope of this study contains two different sizes to cavity, shutdown times of the jet. For the larger size of cavity, the results show that, a vortex is induced in the cavity and dominates the pressure distribution on the impinging flat plate. For the smaller size of cavity, the variations of the pressure distribution on the impinging flat plate are uniform. Besides, before and after of the closure of the jet, the pressure distributions in the cavity vary drastically fromt he negative to positive values in spite of the space of the cavity.