Browsing by Author "Krafft, Douglas"
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Item Drifter study of circulation near Indian River Inlet, DE(University of Delaware, 2017) Krafft, DouglasCurrent patterns were investigated to the north of the stabilized lower-mesotidal Indian River Inlet located on the Delaware Atlantic Coast with Lagrangian drifter measurements and numerical model simulations. A suite of GPS-tracked current-following drifters were deployed north of the Indian River Inlet, near the site of severe and chronic downdrift erosion and numerous sediment nourishments. Over four field experiments drifters measured flow patterns to the north of the Indian River Inlet, collectively spanning the semi-diurnal tidal cycle. Current patterns sufficiently before or after flow reversal within the inlet were found to vary with tidal phase. Hydrodynamics near the inlet were simulated during drifter field experiments and the Eulerian current meter deployments of a previous study using a 2D dynamically coupled Delft3D-FLOW and DELFT3D-WAVE model of the Delaware Atlantic Coast and Delaware Bay. Simulation water levels, velocities, significant wave heights, peak periods, and wave directions were validated with data collected near the inlet, yielding validations of mean Willmott score 0.54 ± 0.25. Simulated flow patterns were assessed through qualitative comparison with observed drifter tracks to indicate reasonable agreement in the falling tide and conditional agreement during the middle of the rising tide. Numerical simulations indicated that tidal forcing dominates current patterns over the study area. Accurate bathymetry was also determined to be important to hydrodynamic predictions in the area.Item Quantification of Vertical Profiles of Cross-Shore, Swash-Zone Flow in the Near Bed Region Using Particle Image Velocimetry(University of Delaware, 2015-05) Krafft, Douglas;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.