The NASA/JSC rotating wall perfused bioreactor vessel was designed to provide a controllable low shear environment for the culture of mammalian cells on microcarriers in the microgravity environment of space. Sufficient mass transport of nutrients and waste products is essential for the growth and differentiation of cell assemblages. In order to accurately predict the mass transport characteristics of the bioreactor vessel and determine appropriate operating conditions for the proper suspension of the cells, detailed knowledge of the motion of the cell assemblages relative to the fluid phase is required. In the microgravity environment, cell assemblages move under the influence of the pressure gradient, viscous shear, and centripetal acceleration fields. A numerical simulation of the trajectories of spherical particles has been used to predict operating conditions that will adequately suspend the cells while minimizing fluid shear stresses on the cells.
A study of the particle trajectories in the NASA/JSC rotating wall perfused bioreactor vessel was performed aboard STS-85 in August, 1997. Spherical beads of various sizes and densities were used to simulate assemblages of cells on microcarriers in the bioreactor. Bead trajectories were videotaped for numerous operating conditions. A split image optical corrector was used to more accurately determine particle positions in three dimensions.
Results from the flight experiments are compared to numerical solutions. For the moderate Reynolds numbers of interest, the history and lift effects were found to be particularly significant.