Laboratory and Numerical Studies of Hydrodynamics Near Jetties

摘要

Numerical and physical modeling studies were performed by the Coastal Inlets Research Program (CIRP) of the U.S. Army Corps of Engineers to investigate the spatial and temporal behavior of waves and wave-induced currents near jetties of an idealized coastal inlet. Hydrodynamics were examined in the vicinity of two extreme types of jetty structure: a highly absorbing jetty (resembling fairly porous rock rubble structure) and a fully reflective jetty (resembling a vertical sheet pile or caisson type breakwater). Laboratory experiments in a Froude scale of 1:50 were conducted with regular and irregular shore-normal (0 deg) and obliquely incident (20 deg) unidirectional waves. Current and wave measurements were made on the up-wave side and inside the inlet as well as in the bay, along a number of cross-shore and along-shore transects. Wave directions were measured by a remote-sensing video-camera system and Acoustic Doppler Velocimeters (ADV). Numerical modeling was performed with the Coastal Modeling System (CMS) consisting of a two- dimensional circulation model coupled to a spectral wave model. Calculated current and wave fields from CMS in the area around and between absorbing or reflected jetties were compared to measurements. The highly reflecting jetty created a circulation cell on the up-wave side of the inlet, whereas the absorbing jetty did not.