Hydraulic characteristic on flow field and sediment movement inside and outside seagrass fields

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To obtain some information to reproduce the disappearing seagrass field in the sea area, the laboratory experiment and the field observation have been conducted. The suspended sediment concentration among model seagrasses has been measured by using image technique. The distribution of suspended sediment and the grain size could be measured simultaneously. It turned out that the particle size was bigger than medium grain size at the beginning of its movement, the particle of a central particle size moved with the increasing of time. To consider the effect of the movement object into the numerical simulation, the wrapping judgment method was used. A measuring method of fluid motion inside and in the vicinity of porous media of silicon spheres is presented. Sodium iodide solution is used as the refraction index matching fluid. In order to capture pictures, a resolution PIV method Some experimental results on the velocity field and turbulence kinemaatic energy are presented. Structure of the flow field inside and in the vicinity of the porous media is discussed. Moreover generation and dissipation mechanism of the turbulence was discussed.A field observation has been executed over the seagrass field formed at Eigashima beach in Akeshi City. There were a lot of died seagrass because the growing thickly period had been passed at time. There are clear correlations in PH and DO, and it is thought the influence of the photosynthesis in daytime. Moreover, the decrease at flow velocity was observed by the influence of the marine forest in the bottom of the sea neighborhood