A three-dimensional computational fluid dynamics (CFD) model was used to evaluate the time-averaged steady-state flow field within the Anaerobic Digester Basin.
Horizontal and vertical flow velocities within the mixing basin were provided to at select elevations within the mixing tank. The results of the CFD model demonstrated that the tank was indeed well mixed, particularly near the floor of the tank, which is critical for keeping solids well mixed, and entrained in the flow. Part of the design is to have some of the nozzles angled upward to increase mixing at higher elevations in the tank as well, which was shown to be effective in the CFD model. Velocities were presented graphically as contour plots, and elevation-averaged values were also presented.
Though not performed in this project, Alden can also include chemical and/or biological reactions in the CFD models. This can help to determine local reaction rates within the tank, concentration gradients, and what the rate-limiting factor is at any location in the tank. Time-varying simulations can also be run to study influences of different inputs in batch processes.