Experimental study on the growth and conversion of duration- and fetch-limited wind waves in water of finite depth

Abstract

This paper presents laboratory experiment results on the initial growth of wind waves in water of finite depth. Under the action of a steady wind flow, mixtures of duration- and fetch-limited waves were generated over a constant water depth. Variations of dimensionless growth rate data against finite-depth wave age and dimensionless depth for both scenarios are found to be highly depth-dependent; however, the growth rates of duration-limited waves are larger than those for fetch-limited waves. Our experiment showed that when wave age increases up to the so-called critical wave age, wind-induced wave growth reaches a limit due to the depth effect. The critical age values determined in our flume agree well with the theoretical ones. Dimensionless power-law predictions are presented for significant wave height and spectral peak period in each wave regime, based on which a set of time-space conversion relationships is obtained. However, our results suggest different conversion equations for wave height and wave period. Even if our data are obtained in a laboratory environment, the widely-used hyperbolic model fitted over our measurements could forecast available field data with a Scatter Index of 0.06 for wave height and 0.17 for wave period.