Observations on horizontal velocities under waves in shallow water at a wave energy site

Based on a two-year dataset from a bottom mounted ADCP in shallow water the horizontal particle velocities under waves are analysed in this paper. The sensor was deployed at one of the most exposed coastlines of the UK at a prospective wave energy site and good data returns were obtained throughout the deployment period. The distributions of wave heights, periods, and particle velocities are analysed for all observed individual waves. Waves were binned into combinations of a range of wave heights and periods and the average values of the measured peak horizontal velocities per bin are compared against wave theory. Results show that the average of the measured values per bin compares reasonably well against theory, with measured values slightly exceeding the calculated results. Good similarity was observed between shorewards and seawards setting velocities under the waves, with higher values observed for shorewards facing velocities. Distributions of shorewards setting velocities in each bin were analysed with Kernel and Burr distributions providing good estimations of them. The maximum observed velocities for all bins were more than twice of either the average value per bin or the theoretically derived values. Results described here are relevant to stress or fatigue calculations of coastal structures, moorings and cables, aquaculture, wave surge energy converters, or sediment transport studies.