Experiments on Nonlinear Wave Groups in Intermediate Water Depth

Evolution of nonlinear wave groups of various initial envelope shapes is studied experimentally in a wave tank. Experiments are performed for different values of the water depth in the tank. The experimental results are compared with the calculations based on the cubic Schrödinger equation. Qualitatively different results are obtained for water depth values corresponding to different signs of the nonlinear term coefficient in the model equation. In relatively shallow water, the demodulation of wave groups is observed, while in a deeper water the maximum wave height increases along the tank due to the focusing, as expected.