Quantification of Vertical Profiles of Cross-Shore, Swash-Zone Flow in the Near Bed Region Using Particle Image Velocimetry

Krafft, Douglas
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University of Delaware
Erosion is a very real problem facing many beaches. Sediment transport in one particular coastal region, the swash zone, is particularly important for understanding coastal erosion. Sediment transport cannot be measured directly, so velocity and sediment concentration are used. Current meters are unable to measure the entire duration the swash event, and cannot measure sheet flow. Sheet flow is a particularly high concentration, near-bed mode of sediment transport, which is an important part of swash-zone sediment transport. This senior thesis examines the capability of particle image velocimetry (PIV) to quantify near-bed, cross-shore vertical velocity profiles, in the swash zone. Determining velocities in temporal gaps in current meter data, and sheet flow are two particular goals. Data from two laboratory flume based swash zone studies were considered. The first experiment, in the Center for Applied Coastal Research scale flume, involved a dam-break swash event over a slope of coarse sediment in a scale flume. The second involved a series of swash events from waves generated by a wave-maker over a slope of finer grained sediment in the O.H. Hinsdale large wave flume. Camera imagery was processed with PIV to develop vertical velocity profiles. These profiles were compared with velocity measurements from a collocated current meter. The results indicate that PIV is capable of determining accurate velocity profiles, velocity profiles through sheet flow, and velocities earlier and later in a swash event than the collocated current meter.
Research Subject Categories::TECHNOLOGY::Civil engineering and architecture , civil engineering