Multiphase non‐Newtonian effects on pulsatile hemodynamics in a coronary artery

Abstract

SUMMARYHemodynamic stresses are involved in the development and progression of vascular diseases. This study investigates the influence of mechanical factors on the hemodynamics of the curved coronary artery in an attempt to identify critical factors of non-Newtonian models. Multiphase non-Newtonian fluid simulations of pulsatile flow were performed and compared with the standard Newtonian fluid models. Different inlet hematocrit levels were used with the simulations to analyze the relationship that hematocrit levels have with red blood cell (RBC) viscosity, shear stress, velocity, and secondary flow. Our results demonstrated that high hematocrit levels induce secondary flow on the inside curvature of the vessel. In addition, RBC viscosity and wall shear stress (WSS) vary as a function of hematocrit level. Low WSS was found to be associated with areas of high hematocrit. These results describe how RBCs interact with the curvature of artery walls. It is concluded that although all models have a good approximation in blood behavior, the multiphase non-Newtonian viscosity model is optimal to demonstrate effects of changes in hematocrit. They provide a better stimulation of realistic blood flow analysis.

The Effect of Stent Porosity and Strut Shape on Saccular Aneurysm and its Numerical Analysis with Lattice Boltzmann Method

“…A pulsatile inlet velocity was used to reproduce the in vivo measurements of luminal velocity. 22 These waveforms are triphasic pulses appropriate for normal hemodynamic conditions first reported by Mills et al 33 The use of an input transient velocity based on normal physiology is justified by the fact that the inlet boundary condition is applied in the cerebral aneurysm. For average resting conditions, blood flow in the artery is generally laminar 10 ; flow deceleration achieved after peak systole induces laminar disturbed flow conditions.…”

Direct numerical simulation of transitional flow in a patient-specific intracranial aneurysm

“…Establishing adequate computational flow models that are of clinical relevance has been an active area of research the last decades. Many studies focus on the relevance of nonlinear rheology (Johnston et al, 2006;Fisher and Rossmann, 2009;Kim et al, 2008;Gijsen et al, 1999;Lee and Steinman, 2007;Galdi et al, 2008), and perhaps the most active area is interaction between blood flow and elastic vessel walls (Gerbeau et al, 2005;Heil, 2004;Bazilevs et al, 2010). There has been remarkably little focus on the presence of turbulence in cerebral arteries, and the assumption of laminar flow is commonly accepted.…”

Assessment of surface roughness and blood rheology on local coronary haemodynamics: a multi-scale computational fluid dynamics study

“…This is likely due to the instability of the multiphase models at extremes of haematocrit [ 54 ]. Above a certain haematocrit, blood ceases to behave as a fluid and the accumulation of RBCs alters the local haemodynamics in these regions [ 37 ]. This aggregation process is dependent on a range of biochemical factors [ 54 , 98 ], and is not accounted for in the MKM5 model resulting in predictions of high haematocrit/shear (figures 11 and 12 a ) and hence much higher WSS/OSI/NNIF values in these regions.…”

“…Thus, the flow of RBCs can be distinguished from that of the surrounding plasma. These multiphase models often use an Eulerian-Eulerian approach which has previously been used in other simulations [35][36][37][38][39][40] to investigate cardiovascular pathologies, evolving theory developed by Gidaspow [31] with an assessment of drag/lift/mass modelling of RBCs for cardiovascular modelling by Yilmaz et al [34]. An advantage of the multiphase models is their ability to capture local variations in haematocrit (RBC concentration) arising from fluid dynamics and can then apply this to the viscosity of the blood, compared to the assumed uniform distribution of the single-phase models.…”