Laboratory Investigation of Combined Wave and Current Bottom Boundary Layer Flows on a Planar Beach

Modeling combined wave and current flows in shallow water systems present several challenges. Shoaling waves propagate at oblique angles to the shoreline and the underlying bed contours. Long-shore currents generated by waves and other processes such as wind or tides advect the wave driven transport in the down drift direction. The nearshore region is characterized by waves propagating at high angles to the current over variable topography, which presents unique challenges in describing momentum flux and sediment transport not associated with flatbed conditions. The Large-Scale Sediment Transport Facility (LSTF), operated by the U. S. Army Corps of Engineer’s Coastal and Hydraulics Laboratory, is designed to investigate surf zone and near-shore sediment transport processes in combined flows. The 30 m x 50 m basin includes an offshore wave maker and a recirculating system to produce long-shore currents. Recent laboratory work was conducted to examine the wave/current boundary layer using a suite of cross-shore ADVs, wave gauges and a Nortek Vectrino to measure vertical profiles (mm scale) within the wave boundary layer. Comparisons to existing bottom boundary layer models under a variety of wave and current conditions show good agreement within the turbulent boundary layer but diverge in the near-bed viscous region. Model accuracy in the context of waves and currents at high angles and variable intensity will be discussed.