Spatial Regular Wave Velocity Field Measurements Near Submerged Breakwaters

Submerged breakwaters are a possible solution for the prevention of coastal erosion problems. They guarantee increased protection between themselves and the coastline, diminishing the risk of coastline erosion and assisting sand accretion or retention. Their efficiency depends and it's normally evaluated through the knowledge of the incident, transmitted and reflected wave heights. A different approach of the problem can be done through the measurement of incident, reflected and transmitted wave energies using a full energy concept, i.e., through the measurement of the velocity flow field and sea surface elevation for a regular wavelength. The results presented show the variation of the measured kinetic, potential, total and turbulent kinetic energies, as a function of the distance to the submerged breakwater, calculated through the phase-dependant measured velocity profiles and water surface elevation. Laser Doppler anemometry technique was used for measuring flow velocities and experiments were carried out at the wave tank of the Hydraulics Laboratory of the University of Porto's Faculty of Engineering.