本研究利用質點軌跡流場觀察法(PTFV)與質點影像速度儀(PIV)，針對人體主動脈弓(aortic arch)及其三支主要分支血管，壁頭動脈(brachiocephalic artery)、左頸總動脈(left common carotid artery)及左鎖骨下動脈(left subclavian artery)進行研究，利用三種不同主動脈弓模型的窄縮率分別為0%(type 1)、25%(type 2)及50%(type 3)探討動脈粥狀硬化斑所造成的管路窄縮對主動脈弓與其分支血流的影響。為了簡化實驗的複雜度，採用透明玻璃製成之主動脈弓硬彎管模型，工作流體以水與甘油混合代替血液，並將工作流體視為牛頓流體且其黏滯係數為常數。流場溫度維持正常體溫37ºc，僅忽略血管的彈性及血管的錐度，降低影響實驗因素。使用血液泵(blood pump)輸出心臟脈波，頻率為1.2 Hz，Womersley parameter為17.31。觀察管內流場之結構衍化以及量測速度、壁面剪應力分佈和紊流強度分佈與紊流動能分佈。並利用壁面定律(law of wall)驗證此套PIV後處理軟體，在徑向速度很小的情況下，靠近壁面的分析結果符合此定律。在實驗中可觀察到，當管路拱型區窄縮率越高時，流體經過動脈硬化之主動脈弓發生分離現象的特徵時間會提前。分離區從拱型區延伸至降胸主動脈內側壁面，分離區內的流場型態包含分離流、渦漩拉伸等。在主動脈弓(type 1)中，拱型區域中心內側壁面所受到的壁面剪應力最小，加上降胸主動脈之分離流對內側壁面的衝擊，造成低密度膽固醇(LDL)容易在此區聚集產生動脈硬化脂肪塊，使得管路窄縮。隨管路窄縮率升高，而窄縮區的剪應力也會劇烈的增加，此時強大的剪應力會作用在硬化物纖維狀的脂肪斑，與膠原蓋，破壞其組織。一旦組織被破壞，血小板將匯聚在此處並凝結形成血栓，導致血液中的氧氣與養分無法運送到器官造成器官機能衰竭、壞死。

Pulsatile flow characteristics and evolution processes in a model simulating the aortic arch of human being is diagnosed by using the particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). The aortic arch model is made of transparent Plexiglas U-tube which has different ratio with three main branches (brachiocephalic artery, left common carotid artery, and left subclavian artery). Working fluid is used as the mixture by water and glycerol. Pulsatile flows simulating the output of a human heart beat is supplied by a “pulsatile blood pump”. The results of this study are obtained using a 72 strokes/minute (1.2 Hz) stroke rate, a 70 ml/stroke (5 L/minute) stroke volume, and a 45%/55% systole/diastole ratio. The temperature, Womersley parameter and time-averaged Reynolds number are measured as 37℃, 17.31, 2869. During systole stroke, the boundary layer on the inner wall separates from the area near the turning arch to the descending thoracic aorta and three dimensional secondary flows are observed. These characteristic flow structures induce reverse and low speed flows and therefore would increase the probability of plaque deposition around the inner wall of the arch. When the stenosis increases, the separation point would be deferred a little to the downstream area and the timing for separation would be advanced. During the diastolic phase, strong reverse flow is produced in the arch. Measured shear stresses show low values around the branch junctions and particularly high values around the outer wall of ascending aorta and descending thoracic aorta. In the aortic arch model with the atherosclerotic, the maximum wall shear stress appears on the inner wall of the arch might crack fibrolipid plaque and collagenous cap of atherosclerotic plaque and therefore would induce rapid assembling of platelets on the exposed connective tissues, form the thrombosis, and therefore diminish the transport of oxygen and metabolites to the organs.

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