本研究利用質點軌跡流場觀察法(PTFV)與質點影像速度儀(PIV)針對人體腎動脈血管系統(Renal arterial system )中兩支主要分枝血管左腎動脈(Left Renal artery)、右腎動脈(Right Renal artery)進行研究，藉由對於腎動脈模型的實驗，探討真實的動態流場及壁面剪應力對於人體的影響。為了簡化實驗的複雜度，採用透明玻璃製成之腎動脈硬管模型，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、4 L/min入口流量和45%/55%的收縮舒張比。觀察管內流場之結構衍化以及量測速度、壁面剪應力分佈。在實驗中可觀察到，當管路流經分枝時會發生分離現象。分離區發生在左腎動脈及右腎動脈入口處的內壁上，分離區內的流場型態包含分離流、渦漩拉伸等。在左、右腎動脈中，在心臟收縮初期兩血管的內側壁面所受到的壁面剪應力最小，容易造成低密度脂蛋白(LDL)在此區聚集產生動脈硬化脂肪斑塊，嚴重甚至會形成粥狀動脈硬化。左腎動脈及右腎動脈在心臟收縮初期，由於血液直接衝擊外側壁面造成強大的剪應力會作用在血管壁上並破壞其組織。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。

The pulsatile flow characteristics and evolution process in a model which simulate the renal artery of human being is diagnosed by using the particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). The renal artery model is made of transparent plexiglas material which has different dimension with three tubes (abdominal artery, left renal artery and right renal artery). Mixture of glycerol and water at 37oC is used in the experiment as a working fluid to mimic the blood flow. To simulate the pulsating blood as it came out from the human heart, a “pulsatile blood pump” is used. A 72 strokes/minute (1.2Hz) stroke rate, with a volume flow rate of 4 L/min and a 45%/55% systole/diastole ratio is adopted in this study. The temporal/spatial evolution processes of the flow pattern, velocity distribution, and wall shear stress during systolic and diastolic phases are presented and discussed. During the systole stroke, the separation of boundary layer from the inner wall near the branch is shown in the PIV results. These characteristic flow structures induce reverse and low speed flows therefore would increase the probability of plaque deposition around the inner wall of the renal artery. The measured shear stresses around the branch junctions are low while the measured shear stresses at the outer wall of the renal artery are high. The high shear stress at the outer wall of the renal artery might crack the fibrolipid plaque and collagenous cap of atherosclerotic. This would induce rapid assembling of platelets on the exposed connective tissues which form the thrombosis. Furthermore it diminishes the transport of oxygen and metabolites supplied to the organ.

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