Wave-induced pore pressures in submerged rubble-mound breakwaters simulated by a compound Boussinesq model

Abstract

A simple model for predicting the vertical distribution of wave-induced pore pressures inside submerged porous structures is presented. A Boussinesq-type model coupled with a Darcy–Forchheimer equation was used to derive depth-averaged velocities. Then their profile was obtained by a semi-empirical approach based on energy considerations applied on a vertical distribution of the particle velocities induced by nonlinear waves in a free field. Laboratory measurements of hydrodynamic pressures were undertaken in a flume for breaking and non-breaking regular waves. The proposed model was compared with these measurements and to the results of a Reynolds Averaged Navier–Stokes equations model. Good agreement of the proposed model with the experiments was found and very good behaviour when compared with the RANS code. Increased pore pressures were identified during the experiments close to the downstream slope of the mound and a tendency of the pressures to increase with wave steepness. These effects were satisfactorily captured by the model.

Keywords:

• Boussinesq-type model
• coastal structure
• ecological engineering
• Forchheimer flow
• pore pressure distribution
• regular waves
• submerged rubble-mound breakwater

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Acknowledgements

The authors gratefully acknowledge the help of Dr Koftis and Prof. P. Prinos (AUTh) for making available the COBRAS algorithm used in DELOS project.