Directional wave spectra off southeast coast of Tamil Nadu

Abstract

Knowledge on directional wave parameter is important for the design of any coastal structure and estimation of nearshore sediment tansport. The desired degree of detail may vary from the information on predominant wave direction to the complete wave directional spreading. A well established way to describe the energy content in an irregular wind generated surface wave assumes superposition of linear waves and the two dimensional energy spectrum can be conveniently expressed as a product of the one dimensional energy spectrum and its angular distribution function at each frequency. Directional wave measurements were carried out at 15 m water depth off southeast coast of Tamil Nadu during November and December 1995. The analysed data shows that predominant wave direction during the study period was from the sector between 50 degrees and 120 degrees . The mean wave direction is found to be the more representative index than the principal wave direction and the mean spreading angle and the directioal width showed similar values. It is found that the values of directional spreading parameter 'S sub(2)' are anways more than 'S sub(1) ' and the average value can be used for modelling the directional spectra.