水面冷却対流の解析手法と鏡ダム湖の水面冷却対流

概要

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Two methods of the cooling water surface convection, namely Kimura's One-Dimensional Convection Method and Energy Method, are investigated to reveal the thermal structure in the boundary layer and to estimate the surface water falling flux. The methods are applied to the vertical water temperature distribution data at the lake KAGAMI DAM in Kochi Prefecture, Japan from December 9, 2003 to January 20, 2004. The conclusion is as follows: (1) Thermal convection cooling water surface occurs only when the surface water temperature is higher than 4℃. If water surface cooling thermal flux is the same, regardless of the water depth, the higher the surface water temperature is the more actively convective movement occurs. (2) Cooling thermal energy flux added to the unit area of water surface Q_o during the observation period at the lake KAGAMI DAM was revealed to be from 80 to 320 (Js^<-1>m^<-2>). (3) Surface-cooled sinking flow flux q_b has come out to be from 1×10^<-5> to 5×10^<-5>ms^<-1>, i.e. the transported water from the surface to the deeper layer amounts from 100 to 180 liters h^<-1>m^<-2>, which entrains oxygen from the water surface to the deeper layers. (4) Velocity (u_λ) of the maximum vortex scale which corresponds to the mean depth of the lake (30m) are from 22 to 47mh^<-1>, which means surface-cooled sinking water reaches the lake bottom around from 40 to 80 minutes.
2011-11-15