Experimental and numerical study of the propagation of focused wave groups in the nearshore zone

The propagation of focused wave groups in intermediate water depth and the shoaling zone is experimentally and numerically considered in this paper. The experiments are carried out in a two-dimensional wave flume and wave trains derived from Pierson-Moskowitz and JONSWAP spectrum are generated. The peak frequency does not change during the wave train propagation for Pierson-Moskowitz waves; however, a downshift of this peak is observed for JONSWAP waves. An energy partitioning is performed in order to track the spatial evolution of energy. Four energy regions are defined for each spectrum type. A nonlinear energy transfer between different spectral regions as the wave train propagates is demonstrated and quantified. Numerical simulations are conducted using a modified Boussinesq model for long waves in shallow waters of varying depth. Experimental results are in satisfactory agreement with numerical predictions, especially in the case of wave trains derived from JONSWAP spectrum. •The peak frequency remains unchanged during the propagation of Pierson-Moskowitz wave trains.•The peak frequency decreases during the propagation of JONSWAP wave trains.•A qualitative similarity in the energetic behaviour in different frequency ranges between the two tested spectra.•A slight increase of energy in the peak region for Pierson-Moskowitz wave trains.•By narrowing the spectrum, the real wave shape is closer to the predicted one.