Two-phase blood flow modelling for deep vein thrombosis

One of the most critical region in vessels is where parietal valves are present due to clot and thrombus formation which causes many cardiovascular diseases such as Deep Vein Thrombosis (DVT). In that sense, the most critical blood component is RBCs in vascular system. Unhealty subjects show that RBCs aggregates and becomes gluey increasing its resistance to flow, dynamic viscosity. This incident may lead blood to form clot and thrombus. Therefore, two-phase non-Newtonian flow model is needed in order to simulate the hemodynamics and to observe the aggregation behaviour of RBCs. This study is contributes to literature of Computational Fluid Dynamics (CFD) methods to model blood flow in vascular system by examining two-phase flow for DVT. The aim of this study is to investigate blood flow more realisticly in deep veins by conducting CFD simulations using OpenFOAM, open source CFD software. A realistic model of blood is correlated after experimental data by implementing a non-Newtonian Carreau-Yasuda viscosity model with the model parameters proposed by Jung et al. Although this model is proposed for three-phase flow, it can be also applied for two-phase model of Red Blood Cells (RBCs), which is the main cause to the non-Newtonian behaviour of blood, and plasma as the continous phase in which RBCs are suspended. This model is implemented in OpenFOAM, open source CFD software, to simulate blood flow. At first, the validation of our numerical model is performed in comparison with experimental data. After the validation of our numerical model with experimental data, same model is implemented in three deep vein geometries with venous valves parietal such as deceased cusps, wide open valve and valve with small opening. RBCs aggregation, velocity profiles and pressure contours are investigated in these geometries, representation of deep veins with parietal valves. With the two-phase blood flow modelling, RBCs aggregation becomes traceable in the flow. Therefore, the volume fraction of RBCs in cells over hematocrit (H\= 0.45) are shown in contours to observe critical regions for DVT models. Additionally, Spatial Wall Shear Stress (SWSSG) Gradient index value is studied in all the simulations of DVT cases. This study investigates the proper WSS based index representation for spatial WSS derivations around the critical regions such as near parietal valve.