Experimental Study On Non-linear Wave In Harbor

When waves passe on to the harbor from the open sea, non-linear ingredients strengthen gradually, in particular to longer period waves, non-linear characteristics are more obvious and have important effects on harbor. Due to relatively great sizes in actual harbor , its resonant wave periods and wavelengths are close to wave periods and wavelengths of incidents long waves, which can excite resonant wave and have important influence on breakwaters, morred ship and other structures. Consequently, studying non-linear waves, especially non-linear long waves, has the invital signifinance.In this master dissertation, firstly, the experiment of wave propagation are carried out in wave basin for the purpose of verifying Boussinesq equation computation model. In the next place, according to different locations of model, three experiments of non-linear wave actions on a box-shaped ship are respectively carried out in order to verify coupled numerical model and analysis non-linear characteristics of waves in harbour.The effects of nonlinearity and basin wall reflection on pressure are studied separately in experiment one and experiment two. In experiment one, the nondimensional point pressure distributions on the surface of the model for different wave conditions are presented , the effects of horizontal, vertical, wave periods and wave heights on the different components of pressure are analysed. The results of the two experiments show that with the increase of wave period, the first order pressure decrease and higher order pressure increase, and that the second order pressures can be greater than the first order ones. Moreover, the fourth order pressures can even be greater than the third order ones in experiment two. Therefore, the non-linear characteristics of longer period waves are important factors for port engineering design.The results of experiment three which are accomplished in a closed wave basin show that sub-harmonic surge occures on point pressures and its corresponding period is respectively 2.6s, 3.0s and 3.4s. The reason which possibly produced sub-harmonic surge are analysed separately from incident waves, natural frequency in a harbor basin, self-vibration frequency of the fluid in the gap between hull and vertical wall. The results show that sub-harmonic surge occures on point pressures are induced by three-dimensional effects of the wave basin.