Joint distributions of wave height and period in laboratory generated nonlinear sea states

•The joint distribution of heights and periods of nonlinear wave records is studied.•Experiments carried out in Marintek, Norway and in CEHIPAR, Spain are used in the work.•The results of the joint distributions are compared with the model of Longuet-Higgins (1983).•The joint distributions of heights and periods in the two basins are similar to each other.•At the mode of the density there is a deviation from the theory, especially for large wave steepness.

The main goal of the work is to investigate the joint distribution of the wave heights and periods of nonlinear wave time series obtained in laboratory conditions. Three groups of laboratory experiments carried out in Marintek, Norway and in CEHIPAR, Spain are used in the work. Due to different scales of the generated waves only the series that in full scale have the same distance from the wave maker are compared. For different initial steepness of the produced wave time series the spatial variations of the main sea state parameters, the power spectral density, the joint distribution of wave heights and periods, and marginal distributions of the wave heights and the wave periods are studied. The observed results of the joint distributions are also compared with the theoretical model of Longuet-Higgins (1983). It is found that the observed joint distributions of wave heights and periods in the Marintek and in the CEHIPAR basins are similar to each other. However the results show that close to the mode of the joint density there is a deviation with different degrees of intensity from the theoretical ones, especially for large wave steepness.