Book Description

In this report, wave breaking on a current is examined through physical-model measurements in an idealized inlet with a steady ebb current. Wave and current measurements will be used to evaluate wave dissipation models. The goal of the study is to provide the data to develop a dissipation function for wave breaking on a current that is based on integrated wave parameters, is applicable for arbitrary water depths, and is robust. The motivation for these laboratory experiments was to measure wave breaking in typical coastal inlet conditions. The measurements are being used to parameterize wave breaking for application in numerical wave transformation models, e.g., in the steady-state spectral wave model STWAVE. The data collected and analyzed for this study are an extension of the data set collected by Smith et al. (1998) in the same physical model facility. Smith et al. (1998) evaluated and developed dissipation algorithms using these data. It was found that whitecapping formulations, strongly dependent on wave steepness, generally under-predict dissipation. A relationship for dissipation as a function of wave height squared was developed which gave improved agreement between calculated and predicted dissipation compared to other work. The relationship also worked as well as others in modeling the wave height. The data presented in this report include a larger range of incident waves and ebb currents than the previous data set (Smith et al. 1998). These experiments also include an elliptical ebb shoal seaward of the inlet. The shoal induces depth-limited breaking (in addition to the current-induced breaking in the inlet), which is a typical feature of many coastal inlets. Also, an examination of effects of laboratory scaling was performed.