透水性圓柱群之三維度流場數值模擬

Abstract

本研究針對透水性圓柱體進行三維度流場的數值模擬與分析，進而瞭解圓柱體的受力情形。模式理論方面，係採用有限體積法離散控制方程式，而以k–ε標準紊流模式搭配體積分率法計算含自由液面之紊流流場。此外，孔隙介質流模式被用以呈現水流通過透水性圓柱時的阻水效應。將模擬結果與物理試驗結果相比較發現兩者結果趨勢一致，顯示本研究採用之模式具有一定的適用性與準確性。 經模式驗證後，將應用此模式於不同透水性的單根圓柱體之流場模擬並探討其受力情形，結果顯示圓柱體透水性越大者，其受力越小。在單排透水性圓柱群案例中，將進行不同擺置情境的流場模擬，分別為不同根數、不同間距及不同角度之案例。比較不同擺設之流場流速分佈圖，在各別情境下，發現根數越多、間距越小及角度越小之案例，圓柱群導流效果較明顯，柱後低速區範圍較大，及圓柱群受力程度較小之差異性。另外，比較各情境下圓柱群之受力情形，角度為最顯著的因子。

In the research, it is aimed to investigate the effect of flow through porous cylinders by using the numerical method. A three-dimensional commercial computational fluid dynamic (CFD) software FLUENT is used to simulate the separated turbulent flows around porous cylinders. The standard k–ε turbulence model and the volume of fluid method (VOF) are involved in the simulation. To present the resistance on the fluid by porous cylinders, the porous media theory is adopted herein. It is shown that the simulated results have good agreement with the experimental results. Furthermore, to discuss the resistant force on the cylinders, flows past single porous cylinder with various porosities are tested. It is found that the resistant force is in adverse proportion to the porosity. Finally, a series of single-row of cylinders with various arrangements, i.e. the number of cylinders, the interval between cylinders and the angle between one row of cylinders and one channel sidewall, are discussed. It can be concluded that the resistant forces on the cylinders decrease as the cylinder number increased, the interval between two cylinders decreased and the angle decreased, respectively.