This is a large closed circuit, horizontal water tunnel facility with five 1m long working sections, each of 500mm x 500mm cross-section. Flow uniformity is achieved with a honeycomb section and a series of screens. A 10:1 contraction is used prior to the first working section to further reduce the turbulence intensity by accelerating the mean flow. A maximum flow speed of 775mm/s is achievable in the working sections with the current 53kW AC motor and the in-line centrifugal pump system. The motor-pump system speed is controlled with an ABB Sami GS frequency controller which allows incremental steps in tunnel speed of 1mm/s over the entire flow speed range. A plenum chamber attached to the final working section diffuses the flow and returns it via a 500mm diameter pipe to the pump.A diatomaceous earth pool filter system running in parallel with the main return flow pipework removes contaminants from the water. The filtration can be activated at any time, but is never operated during experiments.
