Two-phase flows (Euler-Euler methods and Euler-Lagrange methods)

In recent years, the application of numerical modeling in fluid mechanics has expanded significantly in various engineering fields, extending its reach to the simulation of fluid dynamics within living organisms. The use of computer models enables virtual experiments to be carried out, providing insights into the description of phenomena and flow conditions within the human body. Precise visualization of velocity and pressure fields derived from flow simulations holds great promise for identifying areas susceptible to pathological changes, such as plaque accumulation leading to cardiovascular disease. This study attempts to explore the potential of computational fluid dynamics to mimic multiphase blood flow within blood vessels and microchannels. Through numerical analyses of blood flow within the right coronary artery and microchannels with hyperbolic constrictions of varying sizes, blood is considered as a nonhomogeneous mixture consisting primarily erythrocytes and plasma. A numerical model of coronary blood flow has been developed using the Euler-Euler two-phase approach, which accurately represents the interactions between plasma and erythrocytes. Of particular note is the pronounced interaction between these constituents in narrower vessels, where the Fåhræus-Lindqvist effect is manifested, indicating the tendency of erythrocytes to migrate toward the vessel core. The dynamics of particle flow is influenced by the granular temperature, which represents the energy associated with the random motion of the particles. To improve accuracy, the granular temperature equation was adapted using user-defined functions. At the microscale, the numerical model simulates the flow of dextran, as a surrogate for plasma and erythrocytes, within microchannels characterized by hyperbolic constriction and the formation of a cell-free layer. Using both Euler-Euler and Euler-Lagrange hybrid multiphase modeling approaches, the simulation results were validated against in vitro experimental data. The simulations were performed using the commercial software ANSYS Fluent (ANSYS Inc., USA).