震波管與垂直壁面交互作用之數值模擬分析

震波在空氣中以超音速傳導，遇到物體時會造成相當嚴重的破壞力，且在這過程中包含了震波∕震波、震波∕渦漩相互作用的複雜現象。本研究主要透過數值模擬方式，了解渦漩與反射震波交互作用之流場結構。使用有限體積法解算二維非黏性流體的Euler方程式暫態流場。為了驗證程式的正確性，將計算結果與實驗結果比對，獲得良好的結果。本文針對不同的入射震波馬赫數和改變管口與壁面之距離等不同的案例作比較。管口與壁面距離較短的案例中，反射震波還未離開壁面造成負壓，即受到環形震波的交互作用衝擊壁面，進而產生第二局部高壓。研究中發現當初始高壓大於5atm時，由於震波後方高速氣流(到達音速)阻礙反射震波前進，導致壁面上無法形成負壓；管口與壁面距離對於太短，會導致反射震波提早與渦漩交互作用，因此壁面尚未形成負壓，即受到兩道環形震波交會並衝擊。透過本研究可了解震波在衝擊壁面時所產生許多震波交互作用的複雜現象，可在工業界或軍事上震波之應用參考。

關鍵字

數值方法；有限體積法；震波管；渦漩；震波繞射；反射作用

並列摘要

Shock wave propagates in air with supersonic velocity. The serious destroy would be occurred while it impact on the obstacles. Besides, some complex phenomena, the interaction between shocks and between shock/vortex, also are generated in the interacting process. In this study, numerical method is applied to simulate and analysis the flow structures in the interaction between vortex and reflected waves. This study investigates the behavior of shock waves by employing the finite volume method to solve the associated two-dimensional, time-dependent, inviscous flow Euler equations. Meanwhile, proof of the numerical results indicated that those results were in close agreement with the experimental data obtained for the shock wave. Several incident waves with different Mach number and distances from tube to wall are simulated and compared. In the results, the reflected wave impact on the wall in the interacting with ring shock before the reflected wave left wall region and formed negative phase while the distance between tube and wall is shorter. Meanwhile, the impact in this process generates second local high pressure. Furthermore, in these cases we find, if the initial pressure is higher than five atm, the supersonic flow behind shock wave would obstruct the movement of reflected wave, and the negative could not be formed on the wall. In addition, if the distance is too short, the reflected wave interacts with the vortex, and two ring shocks collides each other before the negative phase generated on the wall. This study provides the complex phenomena of blast wave and its effects while it impact on wall. The results also could be used in the industry and military during developing safety assessment and disaster prediction techniques in the supersonic and explosive fields.

並列關鍵字

CFD ； Finite Volume Method ； shock tube ； vortex ； shock diffraction ； shock reflection

參考文獻

12.Chang-Hsien Tai, Shi-Wei Lo, Jr-Ming Miao, Yao-Kuang Su, 1999, “Numerical Study of Muzzle Transient Flow of Howitzer with Muzzle Brake,” The Chinese journal of mechanics Series B, Vol. 22 No. 2, pp. 111-125

1.Daniel, R. Kirk, Joel, M. Faure, Hector Gutierrez, Stanislav, I. Svetlov, Ronald, L. Hayes, and Kevin, K.W. Wang, 2008, “Generation and Analysis of Blast Waves from a Compressed Air-Driven Shock Tube,”AIAA 2008-3847.

4.Howard, L. and Mathews, D., 1965, “On the Vortices Produced in Shock Diffraction,” J.appl. Phys., Vol. 27, pp. 223-231.

5.Schardin, H., 1954, “Measurement of Spherical Shock Waves,” Communications of Pure and Applied Mathematics, Vol. 7, pp. 223-243.

8.Igra, O., G. Hu, J. Falcovitz, and W. Heilig, 2003, “Blast Wave Reflection From Wedges,” Journal of Fluids Engineering, Vol.125, pp. 510-519

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震波管與垂直壁面交互作用之數值模擬分析

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