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. |