| Title: | SHALLOW-WATER SPECTRAL SHAPES |
| DOI No: | 10.1142/9789812701916_0015 |
| Source: | COASTAL ENGINEERING 2004 (pp 206-217)
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| Author(s): | JANE MCKEE SMITH
Coastal and Hydraulics Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199, USA
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| Abstract: | Laboratory flume observations and Boussinesq model simulations of wave transformation are used to investigate the evolution of spectral shapes in shallow water. Wave spectra of nonlinear, shallow-water waves both inside and outside the surf zone evolve to the same equilibrium shape (single-peak, double-peak, broad, and narrow incident spectra). The equilibrium shape consists of two slopes, k-4/3 for kd < 1 and k-5/2 for kd > 1. Broad incident spectra or multi-peaked spectra evolve to equilibrium over shorter distances than narrow incident spectra. Likewise, the evolution distances shorten as nonlinearity increases. The one-dimensional, time-domain Boussinesq model of Nwogu and Demirbilek (2001) reproduced the spectral evolution both inside and outside the surf zone. The model also simulated the equilibrium range spectral shapes for kd < 1.5. Similar to deepwater spectral evolution, the equilibrium range in shallow water is driven by the nonlinear wave-wave interactions. The evolution in spectral shape from strong harmonic peaks to an equilibrium shape reflects the change in wave shape from a vertical asymmetry to a horizontal asymmetry. |
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