Rheological characterization of cellular blood in shear

A hybrid lattice-Boltzmann spectrin-link (LB-SL) method is used to simulate dense suspensions of red blood cells (RBCs) for investigating rheological properties of blood. RBC membranes are modelled using a coarse-grained SL method and are filled with a viscous Newtonian fluid solution with viscosity five times that of the suspending fluid. Relative viscosities, normal stress differences, and particle pressures are reported for a range of capillary numbers at a physiologically realistic haematocrit value of approximately 42.5 %. Viscosity shear thinning is demonstrated for shear rates ranging from 14 to 440 s^-1 and is shown to be affected by the orientation and bending modulus of RBCs. The particle-phase pressure undergoes a change in sign from positive to negative as the shear rate is increased. The particle-phase normal stress tensor values show that there is a transition from compressive to tensile states in the flow direction as the shear rate is increased. The normal stress differences are notably different from those recently reported for deformable capsule suspensions using a similar methodology, which suggests that the bending stiffness and the biconcave shape of RBCs affect the rheology of blood.