A Study On The Calculation Methods Of Wave Characteristics In Port Basin

In order to reduce impacts of waves on port basins, breakwater is built asprotection in the construction process of the port. The calculation of wavecharacteristics is a very way to evaluate effects of the breakwater, therefore, themethod to calculate wave characteristics is very important.From the open ocean to offshore, especially in port basin, the propagation ofwaves is affected by deformation of shallow water, refraction and bottom friction.Because of the protection of breakwater, waves propagate towards port basin, diffractinto port basin and reflect in the port basin. Under the impact of several effects, thepropagation of waves becomes complicated at the offshore, and also the calculation ofdifficult. The common way to calculate wave characteristics is followed “Code forSea Port Hydrology”, which is calculating diffraction and reflection coefficient ofwaves, then waves characteristics. Due to developments of computers, the technologyof mathematic model has been developed and become a matured method. Physicalmodel, as the closed method to simulate reality is also essential in the study of wavecharacteristics.The results from different methods for calculating wave characteristics aredifferent. Because of time limit, most of the projects, only one method is used. In thisstudy, we take three layout patterns of breakwater, single jetty, twin jetties andisolated breakwaters as examples. By using three different methods combined withmathematical model, and comparing with physical model, we give different resultsfrom these three methods and the applicability of these methods.1. In single jetty breakwater, for good propagations to breakwater protection, inthe calculation of wave characteristics, diffraction dominates, the function ofdiffraction from tradition method, mathematical model and physical model are similar,and the applicability of three methods is also good.2. In single jetty breakwater, for bad propagations to breakwater protection, mathematical model is better than standard method when take into account of theeffect of reflection, diffraction and refraction.3. In twin jetties breakwater, because of the impacts of the direction of thebreakwater, the structure of the port and the construction of the wall, the distributionof waves is complicated. Results from the standard method and mathematical modelare different, so it is better to use physical model.4. In isolated breakwater, inside of the protection from breakwater, diffraction ofwaves dominates, so both the standard method and numerical model show the effectof protection.5. In isolated breakwater, outside of the protection from breakwater, mathematicalmodel can show the function of reflection and the change of depth of water. However,with tradition method, the result from wave diffraction has big error, so wavereflection and the impact of water depth change have to be calculated separately.6. When wave overtopping occurs, wave characteristics in front of theconstruction for the port can not be calculated only with standard method ormathematical model, the structure of the construction and the water depth changehave to be considered.