As mentioned above the motion and deformation of RBCs in the blood flow can be regarded as a kind of FSI problem. The study of the dynamics behavior of the RBCs is of great importance due to their high density (≈ 5 × 106/mm3) as well as their vital role in carrying the oxygen from lungs to every cell in the body. The behavior of aRBC depends strongly on the blood vessel diameter. In vessels with diameters greater than 200 m, the blood flow can be accurately modeled as a homogeneous fluid flow. However, for smaller vessels such as capillaries it becomes more appropriate to consider the RBCs as discrete fluid capsules suspended in the plasma. Intensive research has been carried out to study the blood flow behavior in large arteries. On the dynamics of the RBCs in the capillaries, however, there are far fewer experimental and/or numerical investigations. For a sophisticated review of the recent experimental,theoretical, and computational studies of RBCs and their mimics,vesicles and capsules in fluid flow one may refer to used a hybrid LBIB-finite element method to simulate the three-dimensional (3D) tank-treading and tumbling motions in dense RBC suspensions in an external shear flow, where the shear flow was realized by moving the bottom and top walls in opposite directions.