Theoretical study of spilling wave attenuation by air bubbles, turbulence, and bottom friction

Abstract An efficient energy dissipation model with breaking capability is important for accurate prediction of wave evolution, especially when the wave approaches shallower water. So, energy dissipation models based on spilling breaking waves, bottom friction, air bubbles, and turbulence effects have been reformulated to calculate wave height and wave setup in the surf zone. Reductions in wave height predicted by different models have been investigated previously, considering free parameters among others. However, the present study does not incorporate any free parameters. Due to the air-water mixture in shallow water and the nonlinearity of the model equations, we have used an iterative method, which brings consistency to the measured wave decay and wave setup. Results of our simulation are compared with laboratory experimental data obtained by several researchers. The wave height and wave setup are obtained using a new formulation that improves results in comparison with the experimental data. The measured time-averaged void fractions are also compared with the time-averaged turbulent intensity, although a long spatial lag is observed in the present study. The findings imply the potential impacts of disturbed breaking waves, bottom friction, air bubbles, and turbulence effects in wave damping. The results could be useful for coastal engineers in making strategic plans and designing infrastructure to protect coastal communities against coastal hazards.