CFD calculation of initial dilution

Initial dilution is typically calculated using simple models, such as those implemented in the CORMIX and PLUMES packages, or even more basic formulae such as that of Lee and Neville-Jones. Even the more advanced of these models suffer severe limits to their applicability. As diffuser designs become increasingly complex, and regulators’ requirements more stringent, there is a need to look for more sophisticated and general methods for calculating the dilution of discharges from such diffusers. Computational fluid dynamics (CFD) offers the flexibility to meet this challenge. This study has compared results calculated using CFX with those obtained from CORMIX and a physical model for a simple outfall. The results are encouraging, and suggest that CFD may prove useful and practical in more complex initial dilution applications.