NUMERICAL INVESTIGATION OF VARIATIONS IN WALL SHEAR STERSS DISTRIBUTIONS AT THE DISEASED HUMAN CAROTID ARTERY BIFURCATION

From clinical practice, it is known that the non-divider side of carotid sinus is very sensitive for the development of atherosclerotic lesions. Because of drastic consequences of a severely narrowed carotid artery bifurcation, there is a need for detecting mild stenosis, less than 25% area reduction, in a very early stage of the atherosclerotic disease. Wall shear stress plays a significant role in the formation of early atherosclerotic lesions; however these quantities are difficult to measure in vivo. The computerized simulation of the homodynamic behaviour of blood flow in the 3-D model of 25% and 35% stenosed carotid artery with different varying angles and varying mass flow rates at the entrance of CCA has been studied. The non- Newtonian fluid flow in the carotid bifurcation is investigated by using finite volume method to solve the three-dimensional Navier-Stokes equations coupled with a non-Newtonian constitutive model, in which the shear thinning behaviour of blood is described by the Kuang-Luo (K-L) equations. The results show that at the apex of bifurcation junction, because of noticeable changes in blood flow pattern as well as presence of flow separation, recirculation regions, the probability of deposition of atherosclerotic plaque would increase especially on the posterior wall of carotid sinus, due to low wall shear stress. The presence of stenosis will produce two definite regions in ICA especially near the non- divider side. The first region locates in sinus region which incorporates high WSS and the second region is out of the sinus with low WSS. These considerable variations in WSS and turbulence in downstream of stenosis region can cause a series of non-physiologic phenomena which may ultimately result in brain stroke.

Keywords:

carotid artery , stenosis , wall shear stress