Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2558
標題: 幾何柱體形狀與位置對空穴流場之數值模擬與分析
Numerical Simulation and Analysis of the Cavity Flow Field at Variously Geometric Cylinder and Rearrangement
作者: 高江俊
關鍵字: turbulence;紊流;wake flow;vortex shedding;cavity shear layer;self-sustaining oscillation;recirculation;尾流;渦漩剝離;空穴剪力層;自激式振盪;迴流
出版社: 機械工程學系
摘要: 
本文係以數值模擬空穴流場物理特性與各種幾何柱體之形狀對空穴流場影響分析。利用計算流體力學PHOENICS套裝軟體,並依照SIMPLEST計算程序求解,模擬空穴在各種柱體之物理尺度與輪廓變化影響下之二維流場,期能了解空穴上方剪力層的振盪性質及空穴內迴流區結構與幾何形狀柱體之尾流狀態關係。本文所模擬流場之參數如下︰流體入口自由流速(U∞)﹑空穴尺度之長深比(L/D)﹑幾何柱體形狀(Shape)﹑幾何柱體特徵尺寸(d/D)﹑幾何柱體與空穴相對水平位置(XL.E/L)及幾何柱體與空穴相對垂直位置(H/D)。
由數值模擬分析中顯示,當幾何柱體置於空穴上方某一高度時,該尾流區域範圍﹑渦漩結構﹑紊流強度及渦漩流道等確實會對空穴上方剪力層與迴流區造成不同程度之影響。尤其當幾何柱體靠近空穴上游角落垂直距離置於H/D≦1.0與水平距離於XL.E/L≦0.7時,幾何柱體尾流之渦漩剝離及紊流效應與空穴剪力層之不穩定振盪之間彼此產生強烈的交互作用。綜合上述觀點及流場所具物理特性現象,其幾何柱體之尾流形態﹑渦漩剝離﹑交替形式渦漩週期﹑空穴間水平及垂直之距離,對於空穴內部的迴流區結構與上方剪力層之物理現象有著極大的影響。

Abstract
In this study, the numerical simulation and analysis method of a computational fluid dynamics (CFD) code of PHOENICS and according to SIMPLEST algorithm with the Hybrid Scheme was used to calculate the two-dimensional cavity flow field and these influences of the contour, the characteristic scale, the rearrangement of variously geometric cylinder upon the cavity flow field, which had be described and analyzed in the qualitative analysis of these physical properties of the cavity flow field. The simulated parameters in this study were described as follows: inlet work fluid of free stream velocity (U∞), length/depth ratio of cavity (L/D), shape of geometric cylinder, horizontal distance between geometric cylinder and cavity (XL.E/L), vertical distance between geometric cylinder and cavity (H/D).
From the calculating results of the numerical simulation and analysis show that the upper shear layer and inner recirculation zone was effected by these factors of the region of wake flow, the vortex structure, the turbulent strength, and the vortex street of variously geometric cylinder, when the position of geometric cylinder was especially located near the upstream corner of the cavity. The phenomena of strong interaction between the vortex street, turbulent effect of geometric cylinder wake flow and unstable self-sustaining oscillation of the cavity shear layer was shown, when the vertical and horizontal distance between geometric cylinder and cavity are H/D≦1.0, XL.E/L≦0.7, respectively.
From the present study and the phenomena of the flow field show that the upper shear layer and inner recirculation zone structure of cavity are effected by the wake flow, vortex shedding, vortex period of geometric cylinder flow field, and vertical and horizontal distance of between geometric cylinder and cavity. The findings herein establish a fundamental numerical study of two-dimensional cavity flow field at variously geometric cylinder and rearrangement and a basis for further analysis of the associated cavity flow for more complicated cylinder arrangement.
URI: http://hdl.handle.net/11455/2558
Appears in Collections:機械工程學系所

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