Leukocytes dynamics in microcirculation under shear-thinning blood flow

We present detailed simulation results of localised hemodynamics for a cluster of rolling leukocytes under shear-thinning blood flow using a lattice Boltzmann model. Leukocytes were modelled as hard spheres moving through a venule of rigid walls. The used hemorheological parameters were obtained from in vivo measurements in blood samples of Wistar rats. Velocities, shear stresses and torques were computed and visualised for each individual cell, for the cluster and for the fluid. We have found that the flow is mainly three-dimensional due to the swirling and the asymmetry of the formed vortices during the recruitment process. The shear stress is maximum on a cap covering the cell and a cone with its base on the endothelial wall at the contact region. The leukocyte is recruited to the wall with the aid of trapping vortices and four stagnant regions surrounding the cell in addition to lateral motion towards the wall. We suggest that these phenomena are highly dependent on the angular velocity of the leukocyte and on the attractive force between the leukocyte and the endothelial wall. For a moving cluster of recruited leukocytes, velocities and shear stresses as well as torques are computed. It was found that the shear stress at the endothelium gets higher as the cluster moves in the main stream enabling early initialisation of the rolling process.