Optimising Trøjborg retention basin
We examined ways to reduce the amount of contaminants from the retention basin spilling into the harbour during a storm. Using CFD modelling allowed for a detailed understanding of fluid mechanics in the basin. By understanding the flow field, we could make improvements in the ability of basins to settle sediments.
- The basin’s ability to settle these sediments depends on several factors, including:
- the profile of the sediment in the inflow
- the inflow rate
- the geometric features of the basin and spill structure
We used CFD modelling to calculate the 3D dynamics of the flow field within the retention basin during the filling and overflow stages. We then assessed:
- streamlines of the flow paths
- sediment concentration contours
- the quantity of spilled contaminants
By examining critical variables (such as overflow concentrations in a high inflow situation), we can compare the settling effectiveness of various basin designs.
For the Trøjborg retention basin, we found that there is a short flow path between the basin inlets and the spill structure, allowing for a high concentration of sediments near the outlets. In order to lengthen the flow path, we suggested adding baffles (flow directing panels) to the retention basin. This gives the sediments more time to settle, increasing the settling efficiency of the tank and decreasing the amount of sediments that spill out when the basin overflows.