Wave attenuation over porous seabeds: A numerical study

Autor: Maurizio Brocchini, Sara Corvaro, José Carlos Pintado-Patiño, Alec Torres-Freyermuth
Rok vydání: 2017
Předmět:
Zdroj: Ocean Modelling. 117:28-40
ISSN: 1463-5003
DOI: 10.1016/j.ocemod.2017.07.004
Popis: We investigate wave attenuation over porous seabeds by means of a phase- and depth- resolving numerical model that solves the Volume-Averaged Reynolds-Averaged Navier–Stokes (VARANS) equations. The numerical model is calibrated with laboratory data from Corvaro et al. (2010). The numerical model predicts the wave attenuation and the velocity field near the porous bed for different regular wave conditions. Subsequently, a parametric analysis on the physical characteristics of the porous media is made to investigate their relative role on wave attenuation. The results of the analysis indicate nonlinear dependencies of wave attenuation on both, total porosity and mean grain diameter. The widely used parabolic model in terms of the dispersiveness parameter predicts both types of dependencies, effectively. Hence, new parametric formulations are derived for the determination of the coefficients involved in the parabolic model for each type of dependence. On the other hand, the role of the spectral shape on the wave spectrum bulk dissipation is investigated. Numerical results for irregular waves show a clear dependence of the dissipation rate with the Ursell ( Ur ) parameter. The dissipation rate becomes sensitive to frequency spreading for Ur f − 5 tail in the incident wave spectrum underpredicts seabed attenuation with respect to an f − 4 formulation. Finally, bispectral analysis of irregular wave propagation allow us to investigate the mechanism of wave attenuation. The numerical results suggest that energy is directly dissipated at the peak frequency, whereas nonlinear energy transfer plays an important role in energy attenuation at higher harmonics.
Databáze: OpenAIRE
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