Flow-Driven Deformation and Transitions of Healthy and Diseased Red Blood Cells

Red blood cells (RBCs), due to their deformability and membrane complexity, exhibit diverse dynamic behaviors under flow, including tumbling, tank-treading, rolling, stomatocyte formation, and multilobed transitions. These dynamics depend strongly on flow parameters, cell geometry, viscosity contrast, and membrane properties. We present a numerical study of single healthy and diseased RBC dynamics using dissipative particle dynamics (DPD) in both shear and Poiseuille flow. In shear flow, varying capillary number (Ck) and viscosity contrast (λ) yields a detailed phase diagram, reproducing transitions from tumbling to rolling discocyte to stomatocyte and finally multilobe shapes, consistent with the numerical findings of Mauer et al. [Phys. Rev. Lett. 121, 118103 (2018)]. In Poiseuille flow, unconfined simulations show outward migration and stable slippers and croissants, while confinement introduces bistability between these states at high Ck and λ, in agreement with Agarwal and Biros [Phys. Rev. Fluids 7, 093606 (2022)]. These results confirm that DPD models robustly capture RBC dynamics when membrane mechanics, inextensibility, and flow boundaries are treated accurately, providing a foundation for studies of suspension rheology and microcirculation.