内湾の物質分散過程における潮流と恒流の相乗効果 (II)

Abstract

To clarify the water dispersion mechanism in a channel with a complicated coastal geo-metry, some numerical experiments were made with a simple combination of the vortical flowA and the oscillatory flow B (CVOF model). The parameters A and B are the nondimen-sional intensities of these two types of flows which express the constant and the tidal flows inthe actual sea respectively. The followings are found. The coupling of two flows A and Byields the water dispersion. The nondimensional dispersion coefficient D is proportional toA2/B for smaller A/B and to AnB for larger A/B where n is about 2.47. The role of B islike as that of the eddy diffusivity K in the coupling effect of A and K on the dispersion.To examine CVOF model some hydraulic experiments were performed of dye dispersionin a channel, which is partitioned into 6 blocks with narrow openings by water breaksset (jetties) on both side walls alternately. The vortical flow is generated by the oscillatoryflow under the geometric effect of water breaks. It is found that CVOF model explains thepattern and the intensity of dye dispersion in the case when the oscillatory flow B is largeenough and when the opening is narrow enough. The larger dispersion coefficient isobtained for the narrower opening because of the coupling effect.