著者

細田 尚 磯野 太俊

出版者

Japan Society of Civil Engineers

雑誌

応用力学論文集 (ISSN:13459139)

巻号頁・発行日

vol.11, pp.825-834, 2008

被引用文献数

1 1

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This paper describes the fundamental characteristics of vertical heat transfer due to thermal convection during the cooling period (September to February) in the northern part of Lake Biwa. The seasonal variations of the vertical water temperature and water quality distributions are firstly shown with the comparisons of calculated results by 1-D model and observed ones to explain the fundamental features of heat and mass transfer occurring in Lake Biwa through a year. Based on the examination of these results, it is pointed out that the thermal convection during the cooling period is the main mechanisms of DO transfer from the water surface to the bottom of lake. Then the mixing mechanism caused by thermal convection is investigated in detail numerically using 3-D CFD model. It is shown that thermal convection cells are observed in the computational domain, changing the positions of submerging portion temporally and promoting the mixing near the interface between the thermally stratified two layers. It is also pointed out that a fractal structure is observed in the flow generated by thermal convection.<BR>A stochastic model with Monte-Carlo simulation, which is similar to Ising model and forest gap model, is proposed to consider the results of numerical experiments. It is pointed out that the spatial flow structures can be simulated by the stochastic model qualitatively.

著者

細田 尚

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.23, no.4, pp.412-419, 2009-12-15 (Released:2010-06-23)

参考文献数

9

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It is an increasing concern that the depletion of dissolved oxygen (DO) concentration at the bottom layer of the northern-part of Lake Biwa with 100m in maximum depth has been worsen in recent years not only due to eutrophication in water but also the effects of global warming such as the raise of air temperature during winter. Many research have been carried out by various organizations to clarify the mechanism of DO depletion near the lake bottom and to propose the countermeasures. This article firstly describes the seasonal variations of the vertical water temperature and water quality distributions to explain the fundamental features of heat and mass transfer occurring in the northern part of Lake Biwa throughout the year. Since it is well known that the thermal convection during the cooling period is the main mechanism of DO transfer from the surface to the lake bottom, the mixing processes caused by thermal convection are shown using the results of a 3D CFD simulation. Then, the electrolysis of water at the lake bottom for the restoration and DO recovery is introduced as one of the countermeasures proposed by Lake Biwa Environmental Research Institute, Shiga Prefecture. The simulation results of O2 bubble plumes with the dissolution into lake water are also shown under the conditions of laboratory and field experiments.