Investigation of Flow Patterns in Storm Water Retention Ponds using CFD

Abstract

The use of computational fluid dynamics (CFD) as an engineering tool for the design of storm water retention ponds is a rapidly growing area of interest, but there is a large gap in the literature with regard to validating the CFD models against experimental data for investigation of flow patterns and velocity distributions in storm water retention ponds. This paper assesses a CFD model against experimental flow data from a laboratory-scale physical model of an existing field retention pond. The simulated results were compared to each other and also to the experimental data to test the ability of numerical simulations for this type of problem. A representative and realistic range of flow rates from 0.16 to 1.5 L/s was tested in the physical model for comparison with the CFD model. Also, the vorticity from the physical model tests was compared to that from the numerical model to validate the CFD model. The results confirm previous findings that CFD modeling is a potential engineering tool to simulate hydraulics of storm water retention ponds and can reliably be used in pond design even at moderate computational cost. Also, it was found that CFD is relatively insensitive to the turbulence model used and grid density within a wide range of grid densities for observing general flow patterns. However, it is sensitive to the advection schemes for this particular problem. Higher order differencing schemes (high-resolution scheme) worked better than simple differencing schemes like the upwind differencing scheme (UDS). It was also found that the strength of the vorticity increases with increasing flow rate for both models, and at higher flow rates CFD is more consistent in predicting the vorticity than that of the particle tracking velocimetry (PTV) technique used in physical models.