Body force influence on healthy and diseased red blood cell sedimentation using multiphase CFD methods

The accurate simulation of blood, which is a multiphase biofluid comprised of plasma and cellular components, is important for biomedical applications. Computational fluid dynamics is routinely used for blood simulation but traditionally treats the flow field as homogeneous. Red blood cell dynamics and deformation are important as they occupy approximately 45% of the volume in blood and control viscosity and non-Newtonian behaviour. Healthy and diseased red blood cells differ in shape and properties, and an understanding of the behaviour of these cells in flow allows for better insight into in-vitro and in-vivo applications such as early-stage disease identification, non-chemical cell separation, and blood viscosity reduction. A developed lattice Boltzmann-immersed boundary solver with a spring-particle cell model was used to analyse discocyte and echinocyte-II red blood cells moving due to shear flow, settling due to gravitational forces, and moving and deforming due to larger magnetic forces. Echinocyte-II cells were the focus of this work due to their association with early-stage disease. Predicted deformation in shear flow and terminal velocities due to gravitational forces for the discocytes compared well with experimental measurements. The larger deformability of the discocyte cells compared with the echinocyte-II cells for the magnetic force case resulted in larger changes to velocities in the early stages of the simulation due to transient deformability-driven drag modulation, indicating intermittent forces may be useful for non-chemical cell separation. The solver can be considered robust for modelling moving red blood cells and applied body forces can be tuned for accurate cell manipulation applications.