Measurements and Modeling of Long-Period Wave Generated Currents in Port of Long Beach

This paper presents the results of measurements of long-period wave generated currents utilizing a horizontal looking acoustic doppler current profiler (HADCP) coupled with pressure transducer wave gages. The HADCP technology provides an opportunity to directly measure long period wave currents across a basin and provide directional information for the waves which varies by wave period due to varying seiche modes of the basin in the transverse and longitudinal directions. The data also illustrate the sensitivity for wave gage placement in relation to basin seiche nodes and antinodes. The HADCP data were used further to validate predicted wave generated currents from a numerical model of wave hydrodynamics and ship motion resulting from those currents. The ship motion modeling is the most useful for port planning since it is the actual motion of berthed containerships that impacts loading and unloading efficiency and safety. The modeling results suggest a useful tool for assessing potential ship motion issues in the harbor.