Author(s): Munehiro Yamasaki; Hideki Ueshima; Norio Hayakawa; Kazuo Murakami
Linked Author(s): Kazuo Murakami, Norio Hayakawa
Keywords: Modification of flow; Enhancement of water exchange; Stratified bay; Topography modification; Hydraulic model experiment
Abstract: Hydraulic model experiments were carried out by using a rectangular model basin in order to investigate the possibility of modification of flow pattern in a stratified and nearly stagnant coastal water body. In the experiments, we examined the influence of stratified condition on the horizontal circulation flow in a bay and studied the enhancement technique of the circulation flow by the modification of sea bottom topography around the bay mouth. As a result, we found out that there is a difference in horizontal circulation flow in upper and lower layers in stratified condition, and the circulation flow in upper layer is stronger than the one in lower layer. On the other hands, there is no difference in horizontal circulation flow in upper and lower layers in homogeneous condition, and the circulation flows are very weak. We also found that the filling up the deep part around the bay mouth strengthens the circulation flow within a bay and enhances water exchange between bay and ocean waters. The effect of filling the deeper area around the bay mouth is expressed by observing the residence rate and calculating the residence time of floats remaining in the bay. It has been found that the residence time in stratified condition decreases to 1/4 to 1/23by the modification technique of sea bottom, namely filling the hollow around the bay mouth with padding. These results will head to a possibility of improvement of water quality in a bay.
Year: 2001