伊勢湾数値シミュレータの研究第4報 : ゼロ方程式鉛直渦粘性・渦拡散モデルの導入と夏期流動場解析

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We have been advancing a project for a few years from a viewpoint of elucidation of water pollution mechanism in Ise bay. Though we described detailed numerical models for the three dimensional numerical simulator in the previous paper, we remained a problem about a computational method to determine vertical turbulent viscosity and diffusivity. We gave constant values for those parameters as a first approximation and applied the classical equation of Munk and Anderson to take into account an effect of density gradient. Consequently, we neglected the change of those parameters due to velocity shear. In this paper we newly applied Mellor and Yamada level 2 model to computation of those parameters, by which model the log-law distribution of velocity in boudary layers can be reproduced fairy well. We carried out the simulation for 150 tides (about 78 days) by setting parameters in the early summer, using this model. The features of obtained flow structure are summarized as follows ; (1) The strong stratification of water temperature and salinity field are seen from the bay head to the bay center in the vertical section, which vanish or are weakened at north of the bay mouth. (2) The water from Kiso rivers flows from the bay head to the mouth in the upper layer by entraining underlying water, while the oceanic sea water from the bay mouth goes in the middle layer (not the lower layer) to the bay head (i.e., Esturine Circulation). At the sunken basin of the bay center (the lower layer), the stagnation of flow is observed. (3) The flow from Kiso rivers makes clockwise circulations at the bay head and the bay center in the upper layer, which quite resemble the observation data. The streamlines of the circulations are almost parallel to the contour lines of the water surface level (i.e. quasi-geostrophic flow). The flow from the bay mouth constitutes anti-clockwise circulations at the bay head and the bay center in the middle layer, contrary to the upper layer. (4) The relatively strong vertical residual currents is computed in the vicinity of the bay mouth, which is estimated to play an important role for transportation of matter and energy of the bay. Fujiwara et. al (1999) also found similar flow structures as (1) to (3) in the observation data and carried out theoretical considerations. They described the mechanism of generation of such flow structures and concluded those should be universal in small gulf where the bay head is wide compared with the Rossby internal deformation radius (gulf type ROFI).
四日市大学の論文
2000-09-30

伊勢湾数値シミュレータの研究第4報 : ゼロ方程式鉛直渦粘性・渦拡散モデルの導入と夏期流動場解析

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伊勢湾数値シミュレータの研究 第4報 : ゼロ方程式鉛直渦粘性・渦拡散モデルの導入と夏期流動場解析

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伊勢湾数値シミュレータの研究第4報 : ゼロ方程式鉛直渦粘性・渦拡散モデルの導入と夏期流動場解析