3차원 CFD모델을 이용한 정체수역의

Abstract

The total amount of water resources in Korea is 1,240 hundred million tons.

Among the total amount, we use 337 hundred million tons(27%) from lakes, marshes, rivers and underground water. In Korea, there are less natural lakes and marshes because of igneous rock areas. Moreover, we have rainy season in summer so the precipitation is not equal at all seasons. We have to make man-maid lakes and marshes because of these problems.

So, 18,787 man-maid dams, lakes and marshes were built for secure our water resources. These man-maid lakes and marshes are vulnerable to self-purification and can make quiescent water. These phenomenon can occur increment of detention period, thermocline and eutrophication. Also, internal water circulation is not progressed actively when the quiescent water is made. We need to find solutions for Anaerobic condition which can make internal hypoxia level. Because anaerobic condition can aggravate the water quality. Especially, density layers are happen at some storage facilities such as 35 hundred million tons in 79 dams, 32 hundred million tons in 112 reservoirs, 13 hundred million tons in 16 dammed pool irrigations.

This study use a principle for spread of density layer which are mixed surface layer and bottom layer. We selected the Test Bed which can happen density layers in lakes and marshes. And we built 3-dimensional CFD spread model using density current generator which can circulate 100 thousand tons water a day. That water amount is 1/50 of mean low flow of stagnant lakes and marshes. We built the Plant and operated in practice and research the change from water circulation in lakes and marshes DO and temperature. We analyze the spread performance and calculated using CFD model. To plan the density current generator, we have to know amount of surface layer inflow, amount of bottom layer inflow and amount of discharge water. We can get these basic data from CFD analysis directly or indirectly.

Through CFD interpretation, we confirm 1-2cm level flow is headed along the density layer in lakes and marshes which has temperature gradient. We checked the time which the density layer has influenced on the lakes and marshes when we operate the density current generator in Test Bed. We knew the time which surface layer`s water temperature is same as bottom layer`s water temperature using the density current generator. That was occurred during 12-24 hours. In CFD model, it takes 2 hours to finish the whole hydrologic cycle since the density current generator is operated. It has 22 hours differences in reality.

It seems to be that the parameter which turbulent flow and hydraulic and hydrogic in Test Bed is not considered in CFD model.

We have checked the similarity between actual hydrologic cycle by the density current and result of CFD model . Also we can verify the accuracy and credibility.

Finally, this CFD model will be the basic theory for treat of thermocline cause of quiescent water.