New version of SWAN model includes the wave diffraction effect which is the main improvement compared with the previous versions.Experimental data collected in the wave basin of the University of Delaware were used to test its performance.Wave heights were compared in the four cases(with different wave energies and directional spreading spectra).The results agreed well with the measurements,especially for the broad directional spectra cases.The effect of wave diffraction was analyzed by switching on/off the corresponding term.By introducing the diffraction term,the distributions of wave height and wave direction were smoothed,especially obvious for the narrow spectrum cases.Compared with the calculations without diffraction,the model with diffraction effect gave better results.
从三个角度论述虚拟现实(V irtua l R ea lity,VR)和地理信息系统(G IS)集成的必要性,通过对集成方法的归纳,提出4种集成方式,并详细介绍了各自的结构体系和具体特征。在此基础上划分了VR与G IS系统集成的4个阶段,分析当前系统集成现状,指出其发展趋势。同时探讨了VR和G IS系统集成中存在的关键问题,包括数据、虚拟景观技术、VRG IS网络化等,给出目前解决这些问题的一些建议和具体途径。
