In-sewer flow regulators in stormwater management.
The overall aim of this work is to determine the ability of several types of in-sewer flow regulator to limit and attenuate, in conjunction with some type of storage unit, the flow of stormwater into a sewer system. The intended result of these devices is the reduction of overland flooding and downstream surcharge during storm events. Various stormwater management (SWM) techniques, practised both in the UK and
abroad, were reviewed with particular emphasis on attenuation and control. Several types of flow regulators were tested where the choice was based on their popularity (i.e orifice plates and vortex), and novelty (i.e self regulating valve and throttle hose). A full size laboratory rig was built to allow experimentation and comparison of in-situ performance of several flow regulators. This system was capable of generating flows of up to 100 I/s which was controlled by a pneumatic valve interfaced to a dedicated PC. The flow characteristics(discharge and upstream head) were measured efficiently and accurately by two ultrasonic sensors. Investigation of the blockage performance of the vortex flow regulators indicated that these devices retained gross solids at higher heads (i. e. after formation of vortex) which either caused increase in discharge (up to 25% for a given upstream head) or reduced the outlet area (i. e. blockages). In terms of head/discharge relationships, the SRV offered optimum performance with consistent and near constant outflow (discharge changing 3% over 1m change in head). Vortex devices exhibited a linear
relationship which is attributed to small changes in the air-core diameter. Comparisons were also made on the performance of these devices in terms of outlet opening, storage and passage of gross solids. A theoretical model was developed for the vortex regulator by combining the hydraulic properties of the free vortex with Bernoulli's equation and applying the
principle of maximum discharge. In this way discharge could be predicted for a vortex flow regulator with an inlet opening in terms of upstream head and geometry of the device. The model was calibrated using the laboratory data and verified against
independent data sets on blocked devices and from external sources.