No abstract

Artificial reefs have been constructed for protecting coast from erosion and for replacing detached breakwaters . The construction causes topographical change around them. Bottom flow and water surface variation and others caused topographical change. So the experiment using 3-ADV (Acoustic Doppler Velocity Meter) to measure the bottom velocity profile around opening was carried out. And the topographical change by movable bed was investigated.This study shows the result of the distribution of bottom velocity around opening . The result shows that the mean velocity of flow at offshore side of reef was different from that at shore side reef . The former region has cyclic current field. And the change of topographical flux was nearly equals to the calculation results that using the Brown's theory and incident wave conditions.

Artificial reefs have been used to protect coastal erosion, and are now replacing detached breakwaters. When we establish a submerged breakwater or an artificial reef, it is known that a topography change

Artificial reefs have been used to protect coastal erosion, and are now replacing detached breakwaters. Although constructions of the artificial reefs sometimes cause significant score around the reefs, the manuals for the design describe mainly on wave decay. An opening between artificial reefs shows typical scouring likea corn at the offshore of the middle of the opening. To estimate a topographic change, we need the distributions of water surface elevation and the bottoms currents.In this research, we investigated the ability of a fully nonlinear Boussinesq model around anopening with the eddy viscosity model for wave breaking. This paper shows that the numerical results have good agreement with experiments wave surface distributions and bottoms currents.

This research is concerned with the characteristics of wind velocity on through the measurement of wind velocity of nearby sea surface continuously by using a multichannel anemomaster.The main conclusion from this study is as follows; the coefficient of friction calculated by assuming Karman constant as 0.4 ranges between 0.01 and 0.07. Furthermore, there is linear relation between roughness parameter and the coefficient of friction. Wind velocity fluctuation spectra showed that it differs depending upon the height from sea level. A strong eddy occurs at the back of a floating body when the wind velocity measured used in numerical modelling the response of the floating body, which implies that this fact must be taken into account in wind load estimation.