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The red blood cell particle is important in the research studies of blood flow and drug delivery. The biconcave shape makes the motions of the red blood cell particle in fluids more complex than sphere or ellipsoid. Sedimentation behaviors of a red blood cell particle in long circular tubes are investigated by using the lattice Boltzmann method with the Galilean-invariant momentum exchange method. Different blockage ratios and the particle to fluid density ratios are considered. One periodic and two steady sedimentation modes are discovered. When the blockage ratio rises, the motion mode of particles changed from horizontal mode to inclined mode. With the increase of the particle to fluid density ratio, the sedimentation mode changed from the inclined mode to the horizontal mode, and the time of the particles reaching the stable state is obviously distinct in different sedimentation modes. Surprisingly, the oscillatory mode is observed in the larger blockage ratio and lower density ratio of particle to fluid. These works may be able to make active promotions to the research studies of blood circulation of humans.

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