Steady & Transient State Analysis of Non-Newtonian Flow of Blood in Coronary Arteries

Abstract

Cardiovascular disease leading to a heart attack is caused by coronary artery stenosis or obstruction. The change in shear wall stress around the coronary arteries is an important factor in the development of cardiovascular disease. In this work, we analyze the steady and transient behavior of left and right coronary artery blood flow. Then Newtonian and non-Newtonian models have been used to analyze wall shear stress of blood viscosity. Human blood being a non-Newtonian fluid exhibits shear thinning. During the cardiac cycle, it appears as a non-Newtonian fluid with a shear rate between 0.1~100 1/s, while Newtonian fluid exhibiting a shear rate greater than 100 1/s. During the steady-state analysis, the shear stress patterns on the walls in all models were uniform. However, the magnitude of the shear stress of the wall is affected by the model being used. When analyzing transients, blood flow stops and suddenly increases. Therefore, a model using the Generalized Power Law is suitable. Non-Newtonian factors were also analyzed to quantify the non-Newtonian behavior of human blood flow. The Newtonian blood viscosity model is a good approximation of moderately high shear regions; a Generalized Power Law model is recommended to obtain good approximation of low wall shear stress. Fluid Solid Interaction (FSI) analysis of CT scans of left coronary artery was carried out. To study the correlation between the induced flow rates, the tension of the cutting wall and the geometry of the artery; unstable FSI analysis was performed using commercial finite element software to evaluate and measure wall and shear stresses in the system. The left coronary artery is used as a boundary condition and a physiological pressure waveform has been applied. A comparison of results calculated for the FSI model and the solid wall model indicates that the distribution of wall shear stress is significantly affected by the consistency of the walls of arteries.