The longitudinal dispersion coefficient (the one-dimensional diffusion coefficient) in tidal basins: The case of the Seto Inland Sea [Japan]; Significance of matter dispersion due to oscillatory currents
2006
Yasuda, H.(National Fisheries Univ., Shimonoseki, Yamaguchi (Japan))
It was reported in 1970 that the one-dimensional diffusion coefficient (corresponding to the longitudinal dispersion coefficient) of the Seto Inland Sea was 10E7 square cm/s through the analysis of the annually averaged salt budget. Although the coefficient is approximately equivalent to one or a few years of mean residence time of the sea water in the Seto Inland Sea, it is considered to be different from the sea water's own budget, representative of mass transport in the sea water because the salt balance might be much influenced by the density current at the flood season. Since the Seto Inland Sea is a kind of tidal basins, the dispersion coefficient ought to be explained as the dispersion coefficient due to the tidal oscillatory current. Such dispersion coefficient has been being neglected since the report by Holly et al. (1970) where it was rather small in the actual basin. In spite of their report, this study has focused on the tidal oscillatory current as a current inducing effective longitudinal dispersion in tidal basins and analyzed the dispersion process taking account of the new idea that the residual circulation played a role of the lateral mixing instead of the horizontal diffusivity. The longitudinal dispersion coefficient obtained from the present new idea can explain the dye diffusion process in the tidally hydraulic scale model of the Seto Inland Sea, the dispersion coefficient of which is less than 1/10 of 10E7 square cm/s, though the usual idea has not yet been able to explain even such dispersion coefficient.
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