Influences of stenosis and transplantation on behavior of blood flow in the host and grafted vessels using computational fluid dynamics

In this research, the changes of wall shear stress (WSS) of flow blood affected by stenosis and grafted vessels are studied. For the simulation of non-Newtonian fluid, blood in this paper, the Carreau fluid model is used. The severity of the stenosis is considered to reduce the internal cross-sectional area of the host vessel by 30 %. In this paper, simulations are performed on the human body in sports, which are classified into anemia (LHD), normal (NHD) and high blood pressure (HHD). Results are presented in three sections including after stenosis region, transplantation section, and after transplantation region by calculating wall shear stress (WSS). It is reported that wall shear stress is increased after stenosis location due to immediate variation in the cross-section area when blood flows. To explain, Stenosis reduces the cross-section area of the vessel which causes flow contraction. Consequently, this phenomenon increases flow velocity in the central region of blood flow whereas, after passing from stenosis, blood flow is exposed to an abrupt expansion which causes flow back from the central region to wall vicinity in lateral regions of the vessel. Maximum amounts of wall shear stress are achieved at 280 Pa, 350 Pa, and 550 Pa for anemia, normal, and hypertensive individuals in order. However, the consequence of the mentioned phenomenon in hypertensive individuals is more severe than that of anemic ones. Therefore, the geometry of veins is very important in medical surgeries to prevent vessel failure, especially in stressful points of transplantation.