流過一對並列圓柱渦漩逸出流場之數值研究

Numerical study on vortex shedding flows past a pair of side-by-side circular cylinders

林純瑜(CHUN-YU LIN)

指導教授 ： 彭逸凡

國立暨南國際大學/科技學院/土木工程學系/碩士(2012年)

https://doi.org/10.6837/NCNU.2012.00189

摘要

本文以數值分析方法探討流過一對並列圓柱之流場，流場藉由 Navier-Stokes 方程及連續方程求解。對不穩定、具黏滯性且不可壓縮流流場，為求解複雜邊界，採用沈浸邊界法，並配合巢狀網格進行數值模擬。解答過程採用分步法，含複雜邊界之障礙物則以內嵌法處理之，網格系統採用正交、結構化，具局部加密效果之巢狀卡式網格系統。因此，本文首先系統化解析此流過一對並排圓流場，圓場選取雷諾數(Re)介於40~100 之間，以及間距比(G)介於0.4~1.4 間之所有流場。含似單一渦漩逸出、雙渦漩逸出、對稱流場、偏斜流場、抖動、翻拍、穩定狀態、具規則震盪之週期性之渦漩逸出、似週期、混亂渦漩逸出流場等多樣化渦漩逸出流場型態，均出現在本論文中。

關鍵字

巢狀卡氏網格法 ； 內嵌法 ； 分步法

並列摘要

In this paper, a numerical analysis method to investigate the flow through a pair of parallel cylindrical different spacing than the ilk field, flow field is solved by the Navier-Stokes equation and continuity equation. The nested Cartesian grid method is developed for simulating unsteady. In combination with an effective immersed boundary method and a two-step fractional-step procedure, has been adopted to simulate the flows.Therefore,this article first systematic analytic flow through a pair of side-by-side circular flow field, to smooth things over selected Reynolds number (Re) between 40 and 100, and the spacing ratio (G) all of the flow field in the range of 0.4 to 1.4. Contains semi-single vortex shedding street、twin vortex shedding streets、symmetric、deflected、trembled、flip-flopped、steady state、vortex shedding periodically、vortex shedding quasi、by vortex confusion, vortex escape the flow field, such as diversification of the vortex to escape the flow structure, described the development of high efficiency and high accuracy, nested grids.Tested by the nested grid method to flow through symmetrically placed in the channel, the two circular cylindrical obstacle logistics field, to arrive at the average lift drag coefficient, the change of vortex escape, and thus accurately predict the occurrence of vortex escape critical Reynolds number.

並列關鍵字

nested grid method ； immersed boundary method ； Fractional Step Method

參考文獻

1. Peng, Y.F., Shiau, Y.H., Hwang, Robert R., and Hu, C.K., “Multistability and symmetry breaking in the 2-D flow around a square cylinder,” Physical Review E, Vol. 60, pp. 6188-6191 (1999).

2. Peskin, C. S., “Flow patterns around heart valves: a digital computer method for solving the equations of motion,” Ph.D. Dissertation, Departmemt of Physiology, Albert Einstein College of Medicine, University Microfilms (1972).

3. Hirt, C.W., and Nichols, B.D. “Volume of fluid (VOF) method for dynamics of free boundaries,” Journal of Computational Physics, Vol. 39, pp. 201-225 (1981).

4. Ravoux, J.F., Nadim, A., and Haj-Hariri, H., “An Embedding Method for Bluff Body Flows: Interactions of Two Side-by-Side Cylinder Wakes,” Theoretical and Computational Fluid Dynamics, Vol. 16, pp. 433–466 (2003).

5. Choi, J.I., Oberoi, R.C., Edwards, J.R., and Rosati, J.A., “An immersed boundary method for complex incompressible flows,” Journal of Computational Physics, Vol. 224, pp. 757-784 (2007).