بررسي انتقال جرم ذرات LDL در شريان كاروتيد با گرفتگي متقارن تحت جريان نوساني قلب

چكيده انگليسي :

Investigation of LDL mass transfer in Common Carotid Artery with axisymmetric stenosis under the pulsatile flow Sahar Fazli Besheli sunlightsahar@gmail com 2009 05 24 Department of Mechanical engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervoisor Dr Shirani eshirani@cc iut ac irAbstractAtherosclerosis is the condition in which an artery wall thickness as the result of build up fatty materials such ascholesterol describing hardening of medium or large arteries It decreases the elasticity of arterial wall and increasesthe heart pumping of blood In advanced stages ulceration thrombosis occlusion and hypoxia in tissues which arefeeded by the artery results to infarction atherosclerosis occur in special areas of arterial system such asbifurcations curvature and regions of disturbed flow secondary flow and recirculation zone and this indicate theimportance of hemodynamic of flow on generation and development of atherosclerosis In the other hand becauseof this fact that fatty plaques commonly build up of plasma lipoproteins such as LDLs the investigation of masstransfer in artery is an important subject to understand the atherosclerosis phenomena So the investigation of LDLmass transfer in stenosed artery would be the first step to understand the disease process In this study theaxisymmetric arterial stenosis in common carotid under physiological pulsatile flow condition with selectivepermeability of wall for Newtonian and non newtonian model has been investigated using ADINA software NavierStokes and mass transfer equations has been solved using finite element methods The numerical results for an arterywithout stenosis indicates that LDL luminal concentration is about 20 greater than its concentration in bulk flowand the higher the blood pressure and filtration velocity of arterial wall the higher luminal concentration SinceLDLs have different size distribution the physiological range of Schmit number between 1 6 105 and 6 6 105 hasbeen investigated and the numerical result indicated that the larger LDLs the higher the luminal concentration andthe non Newtonian carreau model predict a higher luminal concentration rather than Newtonian model Thenumerical results predict that concentration polarization may also exist under physiological pulsatile flow conditionsand the pulsatility do not diminish this phenomena The time averaged value of luminal concentration is slightlyhigher than that of the corresponding steady flow case In an artery with stenosis under the pulsatile condition despite the result of steady flow the length of recirculation zone do not increase with increasing the local Reynoldsnumber during the time in a cycle because the flow can not adjust itself with the fluctuation of velocity at the inletdue to time limitation In recirculation zone after the throat of stenosis the LDL particles from upstream anddownstream that are carried by back flow accumulate and the peak of the luminal concentration occurs after theseparation point and this results to development of plaque With increasing the stenosis severity before flowseparation the maximum of luminal concentration increases and it reaches to its maximum at separation and thenwith increasing the stenosis severity and length of recirculation zone the maximum of luminal concentrationdecreases This result leads us to estimate the intimal thickening as a function of time until the formation ofatheroma and before the formation of fibroatheroma However it needs comprehensive experimental results Key Words Atherosclerosis Mass Transfer Low Density Lipprotein LDL Pulsatile Flow Carotid Artery Stenosis

فضلي بشلي، سحر

بررسي انتقال جرم ذرات LDL در شريان كاروتيد با گرفتگي متقارن تحت جريان نوساني قلب

آتروسكلروسيس , ليپوپروتئين هاي كم چگال LDL , تصلب شرائين