Experimental study of breaking and energy dissipation in surface waves

We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as $\varepsilon =$H/$\lambda $ (where H is the wave height and $\lambda $ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when $\varepsilon $ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry.