網格交換配合非結構性寬頻元素法於二維不可壓縮流之發展及應用

Development and Applications of Mesh Exchanging with Unstructured Spectral Element Method for Two-dimensional Incompressible Flow

王彥博(Yen-Po Wang)

指導教授 ： 顏瑞和

國立臺灣大學/工學院/機械工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02246

摘要

使用ALE可以處理網格移動的問題，若網格移動範圍太大，會導致網格嚴重扭曲，使得計算的結果不精準。本文針對這個問題以發展ALE運動描述法、非結構性網格之寬頻元素法為核心的程式，加上網格交換，以求解二維不可壓縮層流流場。採用網格交換的方式，可以在網格嚴重扭曲前換上另一套網格系統，使得程式所計算的結果不會因為網格嚴重扭曲而不精準。
本研究利用所發展的程式來探討振幅較大的振動圓柱流，所模擬的實際流場為Re為160、兩圓心距離為3圓柱直徑的並肩雙圓柱在相位角差為180°，振幅大於0.7圓柱直徑之流場，結果發現隨著振幅慢慢加大，鎖頻區的範圍會慢慢縮小，當振幅為0.9圓柱直徑時就沒有鎖頻的現象出現。

關鍵字

網格交換 ； 非結構性性網格 ； 二維不可壓縮流 ； 寬頻元素法 ； ALE運動描述法 ； 圓柱流

並列摘要

A mesh changing algorithm for unstructured spectral element method has been developed for moving boundary problems which usually suffer from large mesh distortions . The main purpose of mesh changing is to ensure the quality of mesh and to keep the accuracy of computation as high as possible when large distortion of mesh occurs. This algorithm was further applied to the study of the phenomena of flow around two side-by-side cylinders with large amplitude of vibration. Incompressible Navier-Stokes equations were solved with ALE dynamics description and Reynolds number of all simulations is 160. Effects of gap and phase difference of vibration between two cylinders were studied. It is found that lock-in area decreases when amplitude of two out-phase(180°) cylinders is higher than 0.7 diameter. And it is also found that there exists limitation of vibration amplitude because lock-in phenomena does not occur any more when amplitude of two out-phase(180°) cylinders is higher than 0.9 diameter.

並列關鍵字

Mesh exchanging ； unstructured element ； two-dimensional incompressible flow ； spectral element method ； ALE ； cylinder flow

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