Calculation Of Depth-averaged Concentration Distribution For Sloped-bank And Experimental Research Of Pollutant Discharged From Corrugated-bank

The diffusion rule of concentration distribution discharged from the vertex of angular area both in academic and practical application has important research significance. In this paper, on the basis of theoretical and experimental research on pollutant concentration distribution discharged from the vertex of angular area for sloped-bank, further analysis was done on the depth-averaged concentration distribution. The paper includes the depth-averaged concentration distribution under the conditions of equal diffusion coefficient and different diffusion coefficient in the transverse and vertical, and preliminary experiment research on the pollutant concentration distribution discharged from the vertex of angular area for corrugated-bank.(1) On the basis of the 3-D concentration distribution analytic solution with equal diffusion coefficient, using mathematical methods in the depth-averaged concentration distribution for theoretical solving. Elicited the computational formulas of depth-averaged concentration distribution, and used the computing method of 2-D concentration field to simulate the longitudinal-transverse distribution after the pollutant diffuse into the water. The results show that the pollutant along the flow direction spread far away after diffusing into the water in the sloped-bank with equal diffusion coefficient, the longitudinal-transverse distribution area of the depth-averaged concentration with the sloped-angle increases gradually reduced, and the shapes of depth-averaged concentration contour map similarity on the same sloped –angle.(2) Based on the vertical 2-D changing slope pollution diffusion experiment device, the experiment uses the tracer(rhodamine B) to simulate the diffusion feature of pollutant in the angular domain for the sloped-bank. In the experiments, the grid oscillation system can make the isotropic turbulent water, the digital image processing technology records the process of pollutant diffusion, and the digital image processing technology is used to obtain the concentration of the different time and space points. Combining the theoretical analysis and experimental results, this paper discusses the depth-averaged concentration distribution with different diffusion coefficient in the transverse and vertical. The results show that spread rapidly along the surface of the water after the tracer into the receiving water, and the velocity of vertical diffusion is slower, the depth line of vertical and average concentration equal points is more and more gentle.(3) In order to better reflect the real bank slope irregularity, altering the sloped-bank into the corrugated-bank and carrying on the experimental research. Analysising the pollutant concentration distribution by observing the experimental photographs and the isoconcentration contour maps which are taken in different grid oscillation frequencies of the corrugated-bank(inclination θ=45°). The result of the experimental study is that the bigger the grid oscillation frequency which in the same diffusion time, the higher the diffusion coefficient, and the faster velocity of the tracer diffusion.The study of the feature of pollutant diffusion and the water environment in the angular domain for the sloped-bank in the project, which has important theoretical significance and practical value for monitoring the shore water environment pollution, and realizing the sustainable development of social economy. so the project has the very broad application prospects.