Spectral wave transformation model for simulating refraction-diffraction with strongly reflecting coastal structures
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Spectral wave transformation model for simulating refraction-diffraction with strongly reflecting coastal structures ZHENG Jinhai1,2∗ , NGUYEN Viet Thanh1,2 , ZHANG Chi1,2 1
2
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China College of Harbor Coastal and Offshore Engineering, Hohai University, Nanjing 210098, China
Received 18 January 2010; accepted 27 September 2010 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2011
Abstract On the basis of the wave action balance equation which incorporates refraction, diffraction, reflection and wave-current interaction, a directional spectral wave transformation model WABED is developed for predicting the irregular wave refraction-diffraction with strongly reflecting structures in coastal regions. In the model, diffraction is taken into account by introducing a term formulated from a parabolic approximation wave equation, and reflection is calculated through a back-marching numerical approach at the reflecting boundary. Two experimental data sets are used to examine the performance of present model with regard to wave characteristics around reflecting coastal structures. One is from a physical experiment at idealized inlet with parallel jetties, while the other is from a laboratory study on a coastal project of the concave breakwater. Reasonably good agreements are found for both cases, revealing the applicability of the present model for predicting combined wave refraction-diffraction processes with strongly reflecting coastal structures. Key words:
1 Introduction When waves propagate towards the shore, their transformation processes often change significantly due to the non-uniform bathymetry such as shoaling, refraction, and breaking, with a result of variation and redistribution of wave characteristics. The case could be largely more complicate when coastal structures exist, where wave diffraction and reflection around structures become dominant. For example, the wave reflection would lead to the concentration of wave energy and local scour in front of a detached breakwater, and the wave diffraction can also modify the wave field and topography behind it. At coastal inlets with jetties, the wave reflection and diffraction have an unneglectable impact on the navigation security and channel siltation. As a consequence, reliable wave prediction is of fundamental importance for such coastal engineering, where wave refraction-diffraction associated with strongly reflecting structures play significant role. Numerical modeling of wave transformation in
nearshore regions has been a widely used technique of continuously increasing interest, because of its lowcost and easy-implementation. For decades, remarkable advances in wave modeling have been made with regard to the improvement of model accuracy or physical completeness. On the other hand, all models have own advantages and limitations, with their applicabilitys in coastal engineering depending on a high degree on the site-specific physical processes a
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