Non-linear transient waves

This dissertation presents the results of a new study on 2-D transient waves, formed through the focusing of wave energy. An extensive laboratory investigation has been undertaken for large number of wave groups with a range of amplitudes and frequency bandwidths. The results show that the focusing of wave energy can produce highly non-linear wave groups, where the nonlinearity increases with amplitude but decreases with increasing bandwidth. The underlying kinematics are also highly non-linear. The results show that linear and second order wave theories may significantly under-estimate both the maximum crest elevations and the near surface kinematics. However, a numerical model, which uses a Fourier series solution and a least-squares minimisation of the free surface boundary conditions, is shown to be in excellent agreement with the measured data.