Research On The Hydrodynamics And Water Displacement Characteristics Of An Artificial Lake Based On The MIKE21 Model

In recent years,with the continuous advancement of urbanization,more and more lakes have problems such as eutrophication,shrinking water area and degradation.The qualit y of lake water directl y affects its ecological environment,and the exchange capacit y of lake water will affect the water qualit y of lake.Therefore,mastering the replacement law of lake water can provide powerful scientific support for improving the water qualit y of lake water.This paper mainl y studies the flow field and water body displacement characteristics of an artificial lake under differ ent water diversion conditions.The main research contents of this paper are as follows:(1)The theory of MIKE21 model is introduced in detail,and a two-dimensional hydrodynamic model is established based on the collected data of an artificial lake.Secondl y,according to the measured water depth and velocit y data at six observation points,t he values of Manning and other parameters are adjusted and determined,and the reliabilit y and accuracy of the model are verified.(2)The changes of water flow field in the target lake under seven diversion flow conditions are studied.The water area with velocit y u<0.0005m/s and u<0.001m/s is taken as stagnant water area,and the relationship between the ratio of stagnant water area to the whole studied water area and diversion flow is studied.The result is that in the initial stage of water diversion,th e areas of two kinds of stagnant water areas are greatl y reduced,and the ratio of stagnant water area to the whole water area is also obviousl y reduced With the continuous increase of diversion flow,the area of stagnant water area and the ratio of stagna nt water area to the whole water area decrease slowl y until it is no longer obvious.(3)The variation characteristics of water replacement rate in this water area under different water diversion time and discharge conditions are studied.The results show t hat with the increase of water diversion time and flow rate,the water body replacement rate first increases greatl y,and then the change trend graduall y stabilizes.With the increase of diversion flow,the time for water body replacement rate to stabilize graduall y shortens.When diversion flow is 15m~3/s,the time for water body replacement rate to stabilize is the longest,about 400 days.When the diversion flow is less than 275m~3/s,the water replacement rate will graduall y stabilize after 50 days of con tinuous diversion.In addition,Within 150 days,the replacement rate of water bodies in the studied waters did not reach 100%,but theoretically,the water bodies in the studied waters could be completel y renewed by prolonging the diversion time or increasing the diversion flow.(4)Under different water diversion time and discharge conditions,the change law of water renewal time in the studied waters was studied.The research results show that the water body renewal time in the study waters decreases with the increase of diversio n flow in the 150-day calculation period.For most of the water bodies in the studied waters,the renewal time of water bodies will be greatl y reduced with a small increase in diversion flow,that is,the renewal time of most water bodies is sensitive to t he change of diversion flow.However,with the increase of diversion flow,the renewal time of water body in lakes and bays does not decrease obviousl y,and the renewal time of water body is relativel y longer.