Various kinds of the very large offshore structures in the enclosed sea are planed or are investigated and the studies of the environmental impact assessment become very important as well as the technology of design and construction of the offshore structures. In marine environmental impact assessment, grasping the change of the tidal current and the residual flow due to the existence of the offshore structure is very important and indispensable to evaluate flow characteristics and diffusion of the pollutant, and furthermore, to assess the change of eco-system. In order to obtain the data, the tidal current simulation using NS equations became popular and important. In this paper, in order to understand the environmental impact from the standpoints of the methodology of reasonable and easy expressions, 1. A particle tracing method by Eulerian-Lagrangian method and calculation results of the seawater exchange and the residence time around an offshore structure in Osaka bay are shown. 2. Application to Kansai international airport (phase 2) are made and compared with the report of the environmental impact assessment. 3. This method is shown practical to estimate the environmental impact of the tidal current.
In Japan surrounded with the sea, having the long coastline, their effective application has been strongly expected and the very large offshore structures like mega-float and so on in the enclosed sea are planned now The tidal current is one of the most important factor of the assessment and these data are applied to estimation of the diffusion of pollutant and impact on eco-system. [1] The tidal current simulations using NS equations have become very popular and advanced according to the development of the computers and massive useful data of the flow fields can be obtained in a very short time.
