(487f) Practical Large Eddy Simulation

A novel approach for performing three-dimensional CFD simulations of bioreactors and fermenters is presented. This approach, which is based on the lattice-Boltzmann model (LBM), eliminates the manual grid meshing process associated with CFD and runs orders-of-magnitude faster than conventional modeling tools. Since the LBM approach conserves energy, it provides direct access to the energy dissipation rates and turbulent energy spectrum at arbitration points across within the domain. Moreover, owing to the explicit time-integration of the flow field, the trajectories and suspension times of bubbles and solids inside the reactor can be modeled directly. Used here to model a 200L and 2000 L agitated fermenter, we predict the effects of impeller speed and off-bottom displacement on blend time, maximum energy dissipation rates, and power draw. We then model the evolution of gas bubbles through the tank and the associated bubble residence time distribution.