Antony, J.Maniyeri, R.2026-02-032025Indian Journal of Physics, 2025, , , pp. -9731458https://doi.org/10.1007/s12648-025-03866-9https://idr.nitk.ac.in/handle/123456789/20597Red blood cell (RBC) deformability is a critical factor in hemorheology, as it directly impacts the ability of RBCs to transport oxygen through narrow capillaries. Reduced RBC deformability, associated with several diseases, results in inadequate blood flow to tissues and organs. Recent studies have highlighted the significance of RBC shape and elasticity in understanding various pathological conditions. Therefore, early detection of diseases associated with RBC deformation is possible by understanding the dynamic behaviour of RBCs. In this study, a numerical model based on smoothed particle hydrodynamics (SPH) is developed to analyze the interaction between healthy and malaria-infected RBCs in Poiseuille flow. SPH is a Lagrangian-based meshless particle method that offers advantages in solving fluid–structure interaction problems with moving interfaces and large deformations. The developed numerical model leverages GPU parallelization, significantly reducing computational costs. The study examines interactions between healthy and malaria-infected RBCs under different orientations to gain insight into their hydrodynamic behavior. The hydrodynamic behaviour of RBCs is significantly influenced by their relative position in the flow. In symmetric orientation, no lateral migration of RBCs is observed, but the shape and deformation differences are more pronounced when the initial distance between them is small. When the RBCs are placed at the same initial lateral position, they separate more if the initial distance between them is small. In different lateral positions, the centre-line healthy RBC is either attracted or repelled depending on whether it is downstream or upstream of the off-centre infected RBC. © Indian Association for the Cultivation of Science 2025.Lateral migrationRed blood cell dynamicsSmoothed particle hydrodynamicsTwo-cell interaction