Abstract
From viewpoints of effective use of coastal sea area, many kind of very large offshore structures in the enclosed sea are planned or investigated, With this tendency, studies of the technology of environmental impact assessment became very important as well as the technology of design and construction of the offshore structules. In a marine environmental impact assessment, grasping the change of tidal current and residual flow due to the existence of the offshore structure are very important and these become necessary basic data to evaluate flow characteristics and diffusion of the pollutant, and furthermore, to assess the chamge of eco-system. The tidal current simulation using NS equations became popular and massive data of flow fields can be obtained for a very short time. In this paper, calculating methods of the tidal current and seawater exchange and their applications are discussed from standpoints of the methodology of easily understandable expression of simulation data. Namely, 1) Calculating method of a particle tracing in the tidal current by the Eulerian-Lagrangian method are investigated. And the seawater exchange and the residence time of particles around an offshore structure in Osaka bay are calculated and compared with the experimehtal results. 2) This method is applied to the tidal flow and seawater exchange around Kansai international airport (phase 2: under construction) and compared with the results of its environmental impact assessment. 3) It is shown that this method is reasonable and easy to understand environmental impact of the tidal flow.
