Optimal designing of animal cell bioreactors by three-dimensional flow simulation using super-computer

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1. We have developed the simulation technique for 3-dimensional flow of a Newtonian fluid in agitated bioreactors using finite element method and supercomputer. Numerical and experimental results were in good agreement with each other concerning velocity and snear stress distributions. Therefore, the technique was found applicable for flow desing of optimal agitated bioreactors.2. It was suggested by this research that there are two manner of cell damage caused by shear stress. One is a critical shear stress which causes cell breakage instantly. The other is a shear stress history for long culture period which causes a decrease of cell viability even if at a lower level of shear stress.3. We have succeeded in estimating a shear stress history in a commercial spinner flask with 2 bladed paddle impellers at the rotational speed of 60 rpm, where the time interval is 0.02 s and the total tracking time is 90 s, by a newly developed particle tracking simulation technique. The particle rotates circularly with gradual going down in the axial direction and then rising upward from the bottom of the flask, and finally almost returns to the initial position. The average of its one cycle time was 30.6 s, and the average of shear stress history per one cycle was 0.134 Pa・s. At next step, it is important to elucidate a relation between the shear stress history and cell damage for long culture time.