COMPUTATIONAL FLUID DYNAMICS MODELLING OF A VEGETATED STORMWATER POND

Stormwater treatment ponds are common, but there are few tools to evaluate their performance. Computational Fluid Dynamics (CFD) is increasingly being used to design and evaluate ponds, but often neglects the effects of vegetation. The Residence Time Distribution (RTD) is an established means of evaluating treatment capability of a pond. This study uses CFD to model vegetated ponds and obtain RTDs. A pond with two different vegetation layouts and also without vegetation is modelled using (i) the Momentum Sink ( MS) approach and (ii) the King, Tinoco, and Cowen (KTC) k-epsilon turbulence model to represent the vegetation in ANSYS Fluent. All five CFD models predict that the majority of residence times are lower than the nominal residence time. Modelling the vegetation has a large impact on the flow field. The MS approach indicates a substantial performance difference due to vegetation. The KTC k-epsilon turbulence, which also includes turbulence generated by the vegetation, shows an even greater difference compared with the empty pond.