This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Motion and distribution of red blood cells in blood microvessels depend on vessel diameter, hematocrit (Hct), RBCs deformability and other factors. Migration of deformable red blood cells (RBCs) to
the center of microvessels and away from the wall leads to the formation of cell-free layer (CFL). Few experiments or simulations considered the effects of motion and interaction of RBCs on CFL thickness. We
employ a meshless (particle) method to model microvascular blood flow. An efficient parallel algorithm is developed for large-scale simulations of blood flow in microvessels. Using the developed method, we
analyze the change in RBCs shape and RBCs distribution and also thickness of CFL in a variety of vessel sizes and Hct conditions. The results indicate that the CFL thickness increases when the vessel size increases
or Hct decreases, which is in good agreement with previous experimental results. We also show change on RBCs shape and distribution for different microvessels diameter and Hct conditions
