  It is important to understand the dynamics of red blood cells (RBCs) in blood
flow. This requires the formulation of coarse-grained RBC models that reproduce
the hydrodynamic properties of blood accurately. One of the models that
successfully reproduce the rheology and morphology of blood has been proposed
by Fedosov et al. [D. A. Fedosov, B. Caswell, and G. E. Karniadakis, Comput.
Methods Appl. Mech. Eng., Vol. 199, 1937-1948 (2010)]. The proposed RBC model
contains several parameters whose values are determined either by various
experiments or physical requirements. In this study, we developed a new method
of determining the parameter values precisely from the fluctuations of the RBC
membrane. Specifically, we studied the relationship between the spectra of the
fluctuations and model parameters. Characteristic peaks were observed in the
spectra, whose peak frequencies were dependent on the parameter values. In
addition, we investigated the spectra of the radius of gyration. We identified
the peaks originating from the spring potential and the volume-conserving
potential appearing in the spectra. These results lead to the precise
experimental determination of the parameters used in the RBC model.
