Energy dissipation of unsteady wave breaking on currents
Abstract
On either a following or an opposing current including blocking conditions, energy dissipation through unsteady wave breaking within a wave group was experimentally investigated. The experiment was conducted by varying wave spectrum slope and current strength. Surface displacements were sampled to examine energy loss and spectral evolution. Two parameters, integral wave steepness and spectral bandwidth, were found to be important to determine the energy dissipation. The spectral bandwidth largely controlled the integral wave steepness at breaking as well as the energy dissipation. Due to wave blocking in a strong opposing current, spectral bandwidth was reduced, resulting in less loss of excess energy fluxes. For a wave spectrum with a flatter slope, a broader bandwidth can be attained so that more energy losses were found. In comparison with the wave spectra before and after the breaker, spectral distribution of energy dissipation was identified. While significant dissipation occurred at the frequencies higher than the spectral peak, a small portion of energy seemed to be gained at the frequencies below the spectral peak. The ratio of energy gain at low frequency components to energy loss at high frequency components tended to be dependent on the breaking severity and the spectral bandwidth. Relatively more energy gain was also found for wave breaking on blocking.
- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2003
- Bibcode:
- 2003APS..DFD.MP006Y