Another one of the Lab's large open channel flow facilities, this flume has the special facility of being able to re-circulate sediment that is transported to the downstream outlet during an experiment.
The flume was built specifically to investigate the transport of riverbed material under uniform flow conditions. The flume has a straight, rectangular section, 11m long and 400mm wide and a variable bed slope up to 1 in 50. Flow spills into a large downstream tank and is re-circulated to the upstream header tank through a 6 inch pipe with flow rates of up to 30 l/s. Sediment that is transported downstream is re-circulated separately from the main flow using a vortex pump which pumps a water-sediment mixture through a 1.5 inch pipe at high velocity.
The re-circulated sediment is reintroduced to the flow at the upstream end of the flume and is distributed across the width of the channel. A V-notch weir is used to measure discharge and bedload transport samples can be collected by intercepting the flow as it spills from the end of the channel. Typical experiments in the flume involve sediment transport measurements, detailed imaging of the bed as it changes through time in response to the transport processes and detailed measurements of the turbulent flow structures near the bed using laser Doppler anemometry (LDA) and particle image velocimetry (PIV).