Investigation of direct numerical simulation and fluid-structure interaction of blood flows over aortic mechanical heart valves

Nowadays, prosthetic heart valves play a very important role in bioengineering, in particular they are employed to replace diseased native heart valves in valvular surgeries to maintain unidirectional blood flow through the heart. However, because of the long-term complications of hemodynamics as well as potentials of blood damage through the prostheses that bring negative effects on the functions of the heart, numerical modelings of the prosthetic heart valves are needed to investigate deeply in order to optimize the designs of the prostheses and prevent them from failures in a long duration. Among the present types of prosthetic heart valves, the bileaflet mechanical heart valve (BMHV) is the most popular one that attracts many in vitro, in vivo and in silico studies worldwide. The computational investigations (in silico) of the aortic BMHV have been doing with a number of numerical methods to quantify hemodynamics and blood damage through the valve. But there is still a dearth of studying in details the hemodynamics and leaflets dynamics at the beginning of diastole and mid-systole. Numerical studies into hemodynamics and hemolysis during tachycardia (phenomena of abnormal fast heart rate) are also lacks in the literature. The real geometry of the aortic root (three-sinuses of Valsalva) is rather limited in previous studies. Therefore, in this current work, a strongly-coupling technique of Fluid-Structure Interaction (FSI) that combines validated numerical methods of Direct Numerical Simulation (DNS) and Immersed Boundary Method (IBM) is presented with the aim of modelling the blood flow over the aortic BMHV and solving the mentioned problems. Hemodynamics over the BMHV with respect to a wide range of cardiac frequency from low heart rates to extremely high heart rates was investigated. The aortic root’s geometry of three sinuses of Valsalva was used to appreciate the effects of asymmetric geometry on the FSI model. The simulation was carried out using the aid of parallel computing to reduce computational cost. The simulation results of leaflet dynamics, velocity profiles of the flow over the aortic BMHV, the contours of the flow velocities, the pressure drops distributions and viscous shear stresses in the whole fluid flow domain inside the aorta at different cardiac frequencies were obtained. The numerical research then could be used as a predictive tool to understand and evaluate the performance of the BMHV in the aorta as well as cardiovascular flow problems that were not considered in other experimental and computational studies.