Hemodynamic simulation in the aortic arch with the lattice Boltzmann method

Abstract

Aortic diseases have high mortality rates, wherein wall shear stress (WSS) and oscillatory shear index play important roles. Previous studies focused on describing the WSS distribution; however, no report has investigated how hemodynamic parameters determine the distribution of WSS. This study investigates the parameters affecting the WSS distribution and determines the variations of these parameters. A realistic healthy aortic geometry is reconstructed from computed tomography medical images, and a flow simulation is performed using the lattice Boltzmann method. The inlet velocity waveform from the Doppler ultrasound measurement is imposed as the inlet boundary condition, whereas the three-element Windkessel model is used as the outlet boundary condition. The measured outlet flow rate waveforms are used to validate the simulation. A good agreement is found between the outlet flow rate waveform obtained from the measurement and that from the simulation: the descending artery, innominate artery, left common carotid, and left subclavian artery receive 63.42%, 24.01%, 4.14%, and 8.46%, respectively, of the total inlet flow rate over the cardiac cycle in the measurements and 62.17%, 24.61%, 4.7%, and 8.44%, respectively, in the simulation. The simulation shows that the temporal and spatial distributions of the WSS are separately determined by the flow rate and impacting angle. The flow rate ratio between the inlet and outlet decreases with an increase in Re. This relation can be fitted well by the exponential function. Moreover, the impacting angle between the blood flow and the vessel centerline is determined by the vessel geometry only.