Numerical Simulation-based Study On The Influence Of Periodic Blood Flow Assumption On Hemodynamic Parameters In The Carotid Artery

Although arterial blood flow is inherently non-periodic under normal physiological conditions,periodic flow assumption has been widely adopted in most hemodynamic studies.It remains unclear how the periodic flow assumption would influence arterial hemodynamics,especially wall shear stress(WSS)and low-density lipoproteins(LDL)deposition that associate closely with endothelial function and atherosclerosis.In this thesis,subject-specific computational models were constructed for sixteen normal carotid arteries based on medical images and measured blood flow velocities.Numerical simulation of blood flow in each carotid artery was performed under measured non-periodic and averaged periodic flow conditions,respectively,with their results being compared to analyze the influences of periodic flow assumption on WSS metrics and LDL deposition.The results showed that simplifying the non-periodic blood flow into a periodic one did not significantly alter the spatial distribution of WSS,but led to various degrees of underestimations of WSS metrics.Specifically,the underestimation for mean wall shear stress(MWSS)was the least(0.5%),the underestimations for time-averaged wall shear stress(TAWSS),oscillatory shear index(OSI)and transversal wall shear stress(trans WSS)were moderate(<10%)and in an acceptable range,and the underestimation for average temporal gradient of wall shear stress(WSSTG)was the largest(27.2%)and was on the order of the magnitudes of inter-subject WSSTG differences.Correlation analyses revealed that periodic flow assumption-induced underestimations of WSS metrics were mainly determined by the non-periodic variation of blood flow velocity(herein quantified by var-V),and in addition a higher internal carotid artery planarity tended to augment the underestimations of WSS metrics.Relatively,the influence of periodic flow assumption on LDL deposition was negligible.The degree of LDL deposition was determined primarily by flow velocity,although the spatial distribution of LDL deposition was remarkably affected by the morphological characteristics(e.g.,bifurcation eccentricity)of the carotid artery.The results of our study suggest that taking the non-periodic characteristic of blood flow into consideration could be important for studying hemodynamics in arteries with a large var-V or specific morphological characteristics,especially when WSSTG is the main hemodynamic parameter of concern.