| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 98 === The pulsatile flow characteristics in a human stent aortic arch has been studied experimentally using particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). Such an aortic arch is modeled using transparent Plexiglas U-tube with three main branches (brachiocephalic artery, left common carotid artery, and left subclavian artery) while the working fluid used to mimic the blood is a 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 set at 37oC, 16.28 and 1148 respectively. 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 phase, the boundary layer at the inner wall separates from the area near the turning arch where the thoracic aorta descends. The induced reverse flow increases the probability of plaque deposition while the strong reverse flow during diastolic phase 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. These results showed a potential risk of atherosclerosis around the junctions of the three branches and aneurysms at the outer wall of ascending aorta. The benefit of placing the stent at the descending thoracic aorta is the decrease of wall shear stress along the aortic arch and three main branches. Furthermore, shaking of wall shear stress decreases with time during systole and diastole cycle due to the present of stent. The present result would be useful for further improvements in placing of stent technology.
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