Laboratory experiments on time-space conversion of wind waves in deep water

Abstract

In comparison to the fetch-limited wave regime, the available data for duration-limited growth condition is very limited. Mutual conversion of these wave regimes is of interest and significance in all of the parametric growth functions proposed so far. Therefore, field-based heuristic relationships have been proposed to convert fetch-limited evolution data into duration-limited domain. However, considering the difficulty of collecting field-based duration-limited wave data, the reliability of the proposed equations is quite questionable. The main aim of this study is to provide experimental measurements describing the fetch-duration conversion of the dominant spectral characteristics of the water waves under steady wind action. The measurements of the present experimentations are supported by the analysis of the energy balance equations governing the wind energy expenditure during each wave scenario. The results manifested the co-existence of two different fetch-duration transition domains for each individual wave height and wave period. Analytical solution of the time-space connecting integral resulted in a conversion equation that was in good agreement with that obtained from the experimental data based on equivalent peak period. It is also demonstrated that although the experiments introduced here were carried out at the initial stages of the wave growth, the obtained results were in good agreement with those reported in more developed growth conditions.