Microgravity offers unique advantages for the cultivation of mammalian tissues because the lack of gravity-induced sedimentation supports three-dimensional growth in an aqueous culture medium. The NASA-designed rotating-wall vessel (RWV), a low-shear, low-turbulence microcarrier culture system rotating a fluid-filled vessel about a horizontal axis, provides a simulated microgravity environment for three-dimensional tissue culture. In this study, the motion of microcarrier particles in the rotating flow of the RWVs has been investigated. Results from theoretical analysis and numerical computations are focused on the motion patterns with the choice of typical parametric conditions. Several parameters of solid/liquid properties and vessel operating conditions are found to affect the migration time of a denser microcarrier to reach the outer wall of the vessel and the shear stress on its surface. A collision model has been applied to account for the interaction of the particles with the wall(s) of the vessel or with each other. Particle-wall and particle-particle collisions affect particle trajectory and increase the instantaneous relative speed and the shear stress on the microcarrier surface. For the interpretation of the detail rotating particulate flow and hydrodynamic environment around the microcarrier, a direct numerical simulation of a finite element technique based on moving unstructured grids has been carried out. With the knowledge of the motion of the fluid and the particles, mass transfer of different chemical species involved in cell culture in the RWV has been studied. The model solves the binary mass transfer equation for the species mass fraction fields. Cell metabolic processes are modeled as chemical reactions with appropriate reaction rates for different species. The transient two-dimensional analysis employed simulates the species diffusion and convection processes, and the temporal and spatial mass fraction distributions are obtained. Mass transfer of different ions from the surface of bioactive glass has also been modeled under both simulated microgravity and normal unit gravity conditions to provide a powerful tool for examining the mechanisms of surface modification of the bioactive glass.