本研究主要發展一套程式系統以求解動態二維斜開瓣於脈動流中之流-固完整耦合問題。仔細驗證脈動血流誘使心瓣運動之非定常特性，以現有之計算流力學(CFD)算則發展求解此一問題之系統模組，應用不可壓縮流之有限體積法求解守恆型式下之Navier-Stokes方程式。為了闡述非停滯狀況下之瓣膜運動，使用結構-非結構耦合格點法(hybrid grid)於每一時間疊代下建構更新網格，並利用單自由度之瓣膜旋轉運動副程式於計算流力算則求解每一時間步階過程中加以耦合計算，同時於每一步階網格運動下嚴格要求符合幾何守恆律(GCL/geometrical conservation law)以免不正確之結果產生。
研究結果顯示，在瓣膜兩側均存在強健之逸放渦流發生，並且一直持續至關閥，這些閉閥渦流(closure vortices)對逆流特性形成強烈之擾動，並且影響後續之開閥流場特性。研究同時應用應力與時間關係之血液損傷指標經驗方程式，結合Lagrangian粒子追踪法去分析流場應力對血球之傷害性。根據本研究所發展出的流-固耦合算則系統分析結果可知，過去文獻以暫態穩定方式去求解不同時序之開閥動態流場象現，其所分析之問題為簡化流場假設，故可能會得到錯誤的結果。

In this study, a fully-coupled two-dimensional fluid-structure interaction software system for a pulsatile flow across a moving tilting-disc valve is developed. Unsteady transvalvular blood flow coupled with induced occluder motion has been examined in details. State-of-the-art computational fluid dynamics (CFD) methods are adopted in the present flow solver development. Incompressible finite-volume method is employed to solve the Reynolds-averaged Navier-Stokes equations in conservation form. To account for nonstationary occluder motion, the meshes surrounding the occluder are generated and updated in each time-marching step using hybrid structure/unstructured grid method. A single-degree-of-freedom rotational occluder model is integrated simultaneously with the CFD time-stepping. The geometrical conservation law is strictly satisfied so as to avoid spurious results generated. It is found in the present study that, on both side of the occluder, strong shedding vortices occur and persist in the valve closing phase. These closure vortices show great influence on the prediction of the regurgitant flow characteristics and the subsequent valve opening dynamics as well. Blood cell damage index developed based on stress-time empirical rule and Lagrangian particle tracking is also introduced to assess the viscous and turbulence-induced stresses effect to the blood cells. Based on the presently developed fluid/structure interaction code, the results obtained from quasi-steady simulations performed at various instants of interest with prescribed occluder motion are critically evaluated to assess whether simplified flow and occluder conditions may lead to erroneous conclusions.

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