High-Fidelity Simulation of Cell Adhesion and Flow with Coarse Grain Modelling: A Numerical and Experimental Approach

A coupled CFD-DEM framework was developed to investigate red blood cell (RBC) transport and cellular adhesion in constricted microchannels, with a primary objective of reducing computational cost while preserving physiological accuracy. Initially, numerical softening factors were implemented, allowing greater overlap between particles to expedite computations, with an optimal value of 0.03 selected. Adhesion forces between RBCs and the channel wall were incorporated, with a minimum effective distance of 0.4{square}{micro}m identified as computationally feasible. However, RBC-RBC adhesion led to artificial clustering and was therefore omitted. Coarse-graining methods were applied up to a factor of 2 to further reduce simulation time, with a value of 1.8 chosen based on consistent cell-free layer (CFL) thickness and drag force characteristics. To correct for the increased drag in coarse-grained models, rolling resistance (Type C) with a coefficient of 0.8 was employed, bringing deviations within 10%. The validated model was then extended to simulate the detachment of adherent C2C12 myoblasts under physiological flow. Experimental validation showed increasing cell retention with seeding time, and simulations reproduced this trend with <5% deviation. The resulting Detachment Force Ratio (DFR) at 6 hours indicates near-equivalence between adhesion and hydrodynamic forces, establishing the models robustness for cell-substrate interaction studies in microfluidics.