Browsing by Author "Fernando, John N"

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    On the characterization of the cavity like flow upstream of the very low head water turbine
    (2013-05-23) Fernando, John N; Rival, David E.
    This thesis presents an experimental investigation into the influence of an upstream obstacle - a backward-facing step - on the performance of the very low head water turbine. Power measurements were used to compare the efficiencies of three different obstacle-turbine configurations. Particle image velocimetry was then used to measure the velocity field directly upstream of the turbine to characterize the loss in efficiency for the smallest obstacle-turbine case. It was found that the velocity profile is highly non-uniform when the obstacle is in close proximity to the turbine, resulting in an uneven and unsteady loading on the blades within the turbine. A second study focused on particle image velocimetry measurements coupled with common-base proper orthogonal decomposition to quantify the flowfield in an idealized cavity-like geometry representative of the obstacle-turbine interaction. These results revealed varying spatio-temporal flow character for increasing cavity aspect ratios.