Abstract
Nowadays, water pollutions in many semi-enclosed bays have been a very serious social problem. In order to solve this problem, we have proposed the method to activate the water exchange between a bay and its outer sea area by using bottom roughness. In thisstudy, we developed two types of bottom roughness and examined their resistance properties experimentally. At first, the bottom roughness which could create the tide-induced residual current normal to the main tidal flow was improved. Then, it was made clear that the bottom roughness with the shape of a quarter sphere had the property to produce directly the tide-induced residual current not only in the parallel direction but also in the arbitrary direction to the main tidal flow. Finally, it was confirmed from the results of the numerical experiment that the combination of these bottom roughness could efficiently make a stronger residual circulation.
