Investigating the flow field of a Stormwater Quality Improvement Device

An experimental investigation was performed on a stormwater quality improvement device (SQID) to analyse the stormwater flow field characteristics and its behaviour in relation to trapping gross pollutants. SQIDs play an essential role in trapping stormwater pollution thus preventing its entry into receiving waterways. A relatively new technology designed to be more efficient than the existing deployment of trash racks. The experimental study is part of an ongoing research to understand the coupling flow phenomenon effect between the flow field and litter accumulation and also to be used as a validation process for Computational Fluid Dynamics (CFD) studies. The experiments consisted of 3D flow field measurements within the chamber of a half scaled model of the prototype SQID using an acoustic Doppler velocimeter (ADV). The experimental study considers the worst case scenario when the device is filled and clogged with litter and this condition is termed fully blocked. For the purpose of conducting measurements, the main flow outlet screens are replaced with solid wall boundaries to simulate the fully blocked conditions and hence the absence of litter particles in the holding chamber permitting the use of the ADV. The results are presented in the form of mass conservation integrals, velocity vectors and streamline visualisation plots. These results aided a better understanding of the flow characteristics and behaviour within the SQID. The findings suggest that when the SQID is fully blocked there is a region of low recirculation near the entry that both helps to retain and prevent entry of the pollutants within the device.