Scale Experiments of a Shallow Channels Impact on Spillway Flow Distribution and Discharge Capacity

This experimental work on discharge capacity investigates the flow distribution in a downscaled, multi-outlet experimental hydraulic rig. The water passing over each individual outlet is gathered and measured separately by collecting it into a large tank suspended on weight cells. This is repeated to ensure repeatability of the mass flow measurement method. To provide a large and robust set of data for CFD validation, six different inflows are tested, ranging from 60 l/s to 180 l/s. The findings show that for a larger inflow, and thus a higher water level, the discharge distribution over the spillway gets exacerbated by increasing the relative differences in the flow through each outlet. The differences in the measured water levels at different points in the channel leading up to the outlets also increase. ADV is used to measure velocities in the flow leading up to the channel for two of the six tested inflows. The ADV data shows persistent recirculation zones in different dimensions, as well as how the flow moving towards the outlets changes subtly as inflow is increased. Finally, comparisons are made to previous experiments on similar setups, indicating that a larger water column under the crest of a spillway reduces risk of uneven flow distribution for a spillway with multiple outlets. The data presented, along with dimensions of the model, can be used as a case study to validate how well different computational methods can predict flow distribution and spillway capacity.