A monolithic fluid structure interaction algorithm applied to red blood cells in a capillary

A parallel fully-coupled fluid-structure interaction (FSI) algorithm [1] has been applied to the deformation of red blood cells (RBCs) in capillaries where cell deformability have significant effects on blood rheology. In the present FSI algorithm, the fluid domain is discretized using the side-centered unstructured finite volume method [2] based on Arbitrary Lagrangian-Eulerian (ALE) formulation, meanwhile the solid domain is discretized with the classical Galerkin finite element formulation for the Saint Venant-Kirchhoff material in a Lagrangian frame. In addition, the compatible kinematic boundary condition boundary condition [1] is applied at interface between the solid and fluid domains in order to satisfy the global discrete geometric conservation law (DGCL). Three important physical parameters for the blood flow are simulated and analyzed (i) the effect of the hematocrit density, (ii) the effect of the red cell spacing, and (iii) the effect of capillary radius. The results show that the cell deformation decreases with increasing hematocrit density which is also shown to play a significant role for velocity field. The capillary diameter is found out to be particularly important for the flow pressure gradient as well as the deformation of red blood cells. The numerical calculations indicate a rather complex shape deformation in which the biconcave discoid shape changes to a parachute-like shape which is in accord with the earlier results in the literature.