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研究生:劉佳興
研究生(外文):Liu, Jia-Shing
論文名稱:主動脈雙葉片人工心瓣脈動流場研究
論文名稱(外文):Pulsatile Flow Past Bileaflet Aortic Valve Prostheses
指導教授:盧博堅盧博堅引用關係
指導教授(外文):Lu, Po-Chien
學位類別:博士
校院名稱:淡江大學
系所名稱:水資源及環境工程學系
學門:工程學門
學類:環境工程學類
論文種類:學術論文
論文出版年:1996
畢業學年度:84
語文別:中文
論文頁數:219
中文關鍵詞:雙葉片人工心瓣脈動流雷諾切應力紊流尺度偏斜流
外文關鍵詞:bileaflet valve prosthesispulsatile flowReynolds shear stressturbulent scaledeflective flow
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本研究針對雙葉片主動脈人工心瓣St. Jude Medical(SJM),
CarboMedics(CM)和Edwards Tekna(modified Duromedics,DM)進行一系列
體外模擬之流體動力學研究。從流體流經心瓣之流場形態、應力分佈及紊
流尺度,來評估這三種人工心瓣的血動力行為。實驗方法採用流場可視化
定性觀察與二分量雷射測速儀 (laser Doppler anemometer, LDA)定量量
測。實驗分為定量流與脈動流流場量測兩大部份。流場的裝置符合幾何相
似及動力相似。定量流之流場為模擬人體主動脈收縮峰期之血流流量,流
量控制在5,10,20,30升/分。量測位置分為上游區、動脈竇區及下游區三
個量測斷面。同時進行放大2.5倍雙葉片心瓣SJM及CM模型之定量流量測,
模擬原型人工心瓣於完全開啟時之30升/分峰值流量。量測範圍著重於雙
葉片間及緊臨葉片下游區域之流場。脈動流場的裝置為體外模擬左心血管
流循環系統,測試邊界條件控制在符合生理脈動波形範圍,維持每分鐘70
下心跳及每分鐘5升之血流流量,而量測斷面均分佈在心瓣下游之動脈竇
區域。 結果顯示,SJM三股孔口射流分佈比較平均,CM之中央孔口射
流有較明顯之偏斜特徵。中央區域由於葉片分離形成兩凹陷尾跡,SJM凹
陷最小,其次為CM和DM。這三種雙葉片心瓣均在動脈竇邊壁之側邊孔口流
邊緣剪力層處形成最大之擾動,而CM及DM於中央區域同樣有較高之擾動應
力。SJM、CM和DM雖同為雙葉片人工心瓣,然彼此呈現不相同流況,此由
於幾何形狀差異、開啟角度差異及支撐移動方式不同。整體而言,SJM之
紊流擾動最小,CM其次,DM具有較大的紊流擾動。以切應力大小評估這三
種心瓣以SJM血動力學最佳。然而此三種心瓣擾動切應力均達到破壞血球
及血小板界限,三種心瓣流場發生最小紊流尺度約為血球之四倍均有可能
與血球直接發生作用,對血球形成破壞。這與臨床上發現之併發症相符。
所以這三種心瓣並非真正理想之心瓣設計。此量測結果可以提供醫生選擇
心瓣的參考。 新一代人工心瓣設計可以參考此三種雙葉片量測結果,
針對其幾何形狀設計之優缺點加以改良。減少流場分離效應,產生較平順
之流動。使心瓣運作機能接近自然心瓣之完美性,達到減少血栓栓塞及免
服用抗凝血劑等目標。
The dynamic performance of the three the three aortic
bileaflet mechanical valves: St. Jude Medical (SJM), CarboMedics
(CM), Edwards Tekna (modified Duromedics, DM) were investigated
in vitro testing. Based on the velocity distribution, the
Reynolds stress and turbulence scales, the hemodynamics of the
valves were compared and evaluated. Downstream of the valves,
flow visualization technique was used to obtain a whole view of
the flow pattern qualitatively and a two-component laser Doppler
anemometer (LDA) was used to measure the distribution of flow
fields quantitatively. All the experiments, set under the
conditions of geometric and dynamic similarities, were performed
in steady and pulsatile flows. A steady flow loop was used to
simulate the peaks of pulsatile flow with flow rate of 5 l/min,
10 l/min, 20 l/min and 30 l/min. The flow fields were measured
upstream of the valves, at the sinus and downstream of the
valves. Hemodynamics performance characteristics of 2.5:1 scaled
models of SJM and CM in steady flow when fully opened were
studied, representing the peak of the pulsatile flow with flow
rate of 30 l/min. Flow fields between the leaflets and
downstream near the leaflets were measured. The pulsatile mock
loop was used to simulate the left side of the human circulatory
system. Test conditions were set at the rate of 70 heart-beats
and 5 l/min. The distribution of pulsatile velocities was used
to measure inside the sinus of the aorta. Results show that
although all the three valves are aortic bileaflet valves, they
have different flow patterns, due to their different opening
angles, leaflet shapes and movements of the hinges. Velocity
profiles showed the most even orifice flow distribution for SJM.
The central jet flows between the leaflets have a deflective
character, in which that of CM is more obvious. Furthermore due
to such flow separation caused by the leaflets, two wakes appear
in the central area. SJM has the smallest wake, CM has a
slightly larger wake, whereas DM has the greatest wake. All the
three valves have the maximum turbulent stresses at the side
flows close to the sinus due to high turbulent disturbance and
large velocity gradient. CM and DM also have high turbulent
stresses occurring at the central region. Among these three
valves, SJM has been found to have the smallest turbulent
stress, CM is slightly higher, whereas DM has the greatest
stress. SJM appears to be best in hemodynamics performance due
to the least Reynolds shear stress and disturbance of flow that
it possesses. The smallest turbulent microscales were found 4
times larger than the blood cell dimension, which could
transform their energy to damage the cell. The levels of stress
that these three valves generate are greater than the threshold
for blood damage and thrombosis hence, resulting in the clinical
complications. The experiment results will be provided for
surgeons to choose the suitable heart valve. Apparently, none of
the valve types is perfect in all hemodynamics testing. By
combining the results above, the new leaflet design of
prosthesis can be made in order to improve the disadvantages of
the present leaflet shape. In order to reduce thromboembolism
and lifelong anticoagulant therapy, the perfect leaflet should
create a flow pattern free from the separation and similar to
the nature flow pattern.
封面
誌謝
中文摘要
英文摘要
待號說明
待號說明
目錄
圖表目錄
第一章 緒論
1-1 心臟
1-2 心臟瓣膜
1-3 人工心瓣
1-4 研究動機
1-5 研究計劃
第二章 文獻回顧
2-1 血球與應力關係
2-2 流場與人工心瓣之作用
2-3 人工心瓣之體外模擬試驗
2-4 脈動資料分析方法
第三章 實驗方法
3-1 流場可視化方法
3-1.1 定量流流場
3-1.2 脈動流流場
3-2 雷射測速儀量測原理
3-3 雷射測速儀量測系統
3-4 觸發信號
3-5 二維雷射測速儀之安裝與測試
第四章 定量流流場研究
4-1 實驗設置及實驗條件
4-2 結果與討論
4-2.1 SJM量測結果
4-2.2 CM量測結果
4-2.3 討論
第五章 放大模型之定量流流場研究
5-1 實驗設置及實驗條件
5-2 結果與討論
5-2.1 流場可視化結果
5-2.2 LCA速度場量測結果
5-2.3 討論
第六章 雙葉人工心瓣脈動速度場及紊流應力分佈之流場研究
6-1 實驗設置及實驗條件
6-1.1 左心室血管流模擬循環系統
6-1.2 流場之量測參數
6-1.3 資料的擷取和分析
6-2 結果與討論
6-2.1 流場可視化結果
6-2.2 LDA速度場量測結果
6-2.3 三種心瓣量測結果之比較
第七章 雙葉片心瓣脈動流場循環間之差異及紊流尺度之研究
7-1 實驗設置及實驗條件
7-2 資料擷取與分析
7-3 結果與討論
7-3.1 紊流速度場的結果
7-3.2 能譜密度函數的結果
7-3.3 時間自相關係數的結果
7-3.4 積分時間尺度與泰勒微時間尺度
7-3.5 積分長度尺度、泰勒微長度尺度及最小紊流尺度
第八章 結論與建議
8-1 結論
8-2 建議
參考文獻
附圖
附錄一 二維雷射測速儀之安裝與測試
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