Phase-Resolved Modeling and Laboratory Investigation of Surfzone Eddies and Transient Rip Currents

Abstract:

Rip currents drive the exchange of pollutants, larvae, and other particulate matter from the surf zone to the inner shelf. While bathymetric rip currents form in known locations, the location and timing of transient rip currents is unpredictable, leading to sparse field observations. Using a combination of laboratory results and a phase resolving, three-dimensional, non-hydrostatic numerical model, Simulating Waves At the Shore (SWASH), surfzone eddy dynamics and their role in the formation of transient rip currents are investigated. SWASH has previously been used to simulate surfzone dynamics, but a detailed study of the cross-shore evolution of wave spectra and cross-shore currents, including very low frequency currents, has not been investigated. Here SWASH simulations are conducted to study surfzone eddy dynamics at the O.H. Hinsdale Wave Research Laboratory’s Direction Wave Basin at Oregon State University. The modeled dynamics for the laboratory barred beach bathymetry are compared with observations for wave conditions with significant wave height from 0.15 to 0.3 m and a directional spread from 10 to 40 degrees. In addition to providing an assessment of the model skill in reproducing laboratory conditions, these simulations will expand the understanding of surfzone eddy dynamics.