Effects of Frequency-Directional Spreading on the Longshore Current

This paper presents a detailed study on the sensitivity of a number of important wave and current parameters (wave height, driving forces, wave-induced current) to the directional and frequency spreading of the random sea. The analysis is carried out using a purpose-built wave and current model. Three forms of input are used, a directional spectrum, a frequency spectrum and a monochromatic wave, corresponding to different sea conditions, short-crested, unidirectional and monochromatic waves. It is concluded that the directional spreading affects radically the wave and current fields. Its effect is much more pronounced on the driving forces and longshore current velocity (differences up to 50%) rather than on the wave heights. Moreover, the obtained results show that the above quantities are not very sensitive to the frequency spreading.