Physical Model Test And Numerical Model Optimization Of Algae-proof Water Intake In Shallow Lakes

Most cities in China take lakes and reservoirs as the drinking water sources,but the eutrophication and algal blooms increasingly threatened the drinking water safety,therefore the research of algae-proof water intake becomes an important project.At present,there are many mature research methods of algae-proof water intake aimed at deep water lakes and reservoirs,however the problem of algae-proof is so far unresolved effectively in shallow lakes.Chosen the proposed water intake of the third waterwork of Chaohu Lake as the prototype,this paper researched the algae-proof efficiency and mechanism of different structures of the dam-board based on the physical model test and numerical model optimization.According to the research result,a new optimal structure of dam-board for algae-proof water intake was developed.Combining the optimal dam-board with algae control technique in situ,the optimized design scheme of algae-proof water intake was put forward that suitable for the shallow-lakes.In this study,the edges,which conected the dam-board and water intake head,were defined as the width of the dam-board and denoted as l.Adjacent edges were defined as the length of the dam-board and denoted as b.Aspect ratio of the dam-board denoted as Ar.The main conclusions of this paper as follow:(1)The algae-proof efficiency of different dam-board structures.From synthetically analyzing experimental results,the algae-proof efficiency was influenced by the shape and aspect ratio of the dam-board.Among the three kinds of shapes: straight,inclined,arc,the algae-proof efficiency of the arc dam-board is the highest and the straight is the lowest;The optimal aspect ratio was 1.The algae-proof efficiency was very low with Ar>1,and it was the positive correlation between the algae-proof efficiency and aspect ratio with Ar<1.(2)The algae-proof mechanism of different dam-board structures.The algae-proof mechanism of the dam-board contained two aspects.On the one hand,the dam-board could be proof against some algaes that carried by incoming flow,according to the result of the physical model test,but this function of algae-proof is secondary;On the other hand,the flow regime was changed by the dam-board around the water intake.The number and intensity of vortex were affected by the shape and aspect ratio.Among the three kinds of shapes : straight,inclined,arc,the number of vortex of the arc and the inclined were more than the straight.No vortex could be formed with Ar>1,and it was positive correlation between the intensity of vortex and aspect ratio with Ar<1.The changed flow regime was beneficial to the algae-proof and it was the main factor for the algae-proof through comparing the efficiency.(3)The optimized design scheme of algae-proof water intake in shallow lakes.The optimal dam-board structure was arc and Ar=1 through the physical model test and numerical model optimization.Based on the optimal dam-board structure,the optimized design scheme of algae-proof water intake was put forward,which contained:enclosureproof,algae control in situ,algae-proof.This scheme was flexible and adjustable to the actual situation,and the multi-level facility could preferably promote the algae-proof efficiency.