Abstract:
The aim of this study is to provide insight to how pulsatile hemodynamics varies with rheology of blood and blood vessel elasticity in case of an abdominal aortic aneurysm (AAA). Fluid-solid interaction method with arbitrary Lagrangian-Eulerian formulation is adopted with the Newtonian, the shear thinning Carreau and viscoelastic modified Oldroyd-B constitutive models to represent the rheological behavior of blood and the linearly elastic and the hyperelastic Yeoh wall models. Finite element based numerical solver is used to investigate the blood flow in terms of axial velocity across the AAA, vortical structure and shear stress acting on the aneurysm. The anomalies in the vascular network are monitored using the risk indices such as the oscillatory shear index and the time-averaged wall shear stress. The investigations are carried out for the purely shear thinning properties of the blood by using the Newtonian and Carreau models with different arterial wall models to compare the output parameters. Newtonian assumption for the blood, and modelling the arterial wall as linearly elastic lead to significant differences in oscillatory hemodynamic properties when compared to the use of Carreau fluid together with the hyperelastic vessel model. The combined ef fects of viscoelasticity and shear thinning properties are investigated by using modified Oldroyd-B, Carreau and Newtonian models. The viscoelastic fluid shows differences in the vortical field, and significantly higher risk indicators compared to the other models. The elasticity effects are further investigated by a smaller aneurysm geometry. The increase in the elasticity changes the vortical structure, and increases the wall shear stress, as well as the risk indicators.
