Set-Up due to Random Waves: Influence of the Directional Spectrum
This paper deals with the estimation of set-up due to irregular waves. Following the logic of Barbaro and Martino [1], it is derived the analytical expression of the set-up. The solution is based on the hypotheses of straight, parallel depth contours and constant average flow parameters in the longshore direction. In this context, the corresponding value of the set-up is calculated from a specified off-shore directional spectrum. The effect of the assumed directional spectrum is investigated. In particular, set-up is estimated by considering the following frequency spectra: Pierson-Moskowitz [2], JONSWAP [3] and Ochi-Hubble [4]. Further, influence of the spreading function is investigated by assuming a cosine-power [5] and a hyperbolic spreading function [6]. It is shown that the assumed off-shore spectrum significantly modifies the estimated set-up. It is proposed a practical application. The estimation has been carried out by considering various Italian and American locations. The model is applied from buoy data, that are provided by ISPRA (Istituto Superiore per la Protezione e la Ricerca Ambientale) and by NDBC (National Data Buoy Center).