單及雙音速噴流流場觀察之研究

Abstract

利用Laser-Induced Fluorescence ( LIF ) 方法，進行單及雙音速噴流交互作用之實驗研究。流場可視化是當今對於流場分析最有效的工具之一，它將有助於讓我們對於複雜流場有更深一層的認識，進而應用其流場的特徵。本論文中，將單一或雙噴流之交互作用進行流場可視化。以喉管為基礎的Knudsen number 下，範圍為 0.0001~0.0039 之間，並觀察在不同的上游停滯壓力跟下游腔體壓力之比，其流場結構的變化情況。由實驗結果得知，在低Knudsen number、高壓力比條件下，其barrel shock及Mach disk shock 皆可清楚地描繪出來，但隨著Knudsen number 的增加、壓力比的遞減而消失成為可壓縮的膨脹流。

Flow visualization is one of the most effective tools in flow analysis, and it has been crucial for improving our understanding for complex fluid flows. In fact, some of major discoveries in fluid mechanics were made using flow visualization. In this study, the flow fields of single or two interacting parallel supersonic free jets are studied by flow visualization using laser-induced fluorescence of iodine molecules seeded in carrier Argon gas. Rarefaction parameter characterized by Knudsen numbers (based on throat conditions) is varied in the range of 0.0001~0.0039, which corresponds to the flow from continuum to continuum regimes. To observe the flow field structures as different ratio of upstream stagnation pressure to downstream chamber pressure. Results show that a distinct barrel shock and Mach disk structure is clearly captured for a single jet flow at low Knudsen number and high pressure ratio , while it is diminished to a purely compressible, expanding flow with increasing Knudsen number. Interaction between two jets is discussed in detail.