| The sloped topography in natural water such as rivers and reservoirs is mostly irregular,but outfall is often on shore in practical engineering,sewage discharge often form the high concentration pollution mixing zone in the shore area.According to the different sloped topographies and turbulent conditions,the study of the periodicity of pollutants concentration distribution of natural water angular field in the pollutant mixing zone of high concentration is the important basis and technical aspects for functional region division,management decision and comprehensive renovation of water environment.Based on the pollutant concentration distribution theory and experimental research results of the angular field of sloped bank,this paper put forward reconstruction plan for the experimental diffusion model,desiged and developed experimental apparatus of vertical two-dimensional groove-in-groove diffusion tank.It was used for simulating the cross sections of rivers which had different diffusion coefficient in lateral and vertical deractions and complex geometry conditions.The designed groove-in-groove structure provideed the static water environment for bank discharge diffusion experiments,solveed problems such as the deformation,displacement and leakage of chemicals,which appeared in previous research models.In addition,it improveed the success rate of the experiment greatly.According to the actual situation of natural rivers and reservoirs,here gave three kinds of the relevant geometrical parameters of complex sloped bank,and designed reasonable inner tank model for the different sloped bank conditions.Under the guidance of the sewage concentration distribution theory of the vertex,the experiment on instantaneous line source emission of pollutant discharge into a sloped-bank angular field from the vertex was carried out by means of experimental apparatus of vertical two-dimensional groove-in-groove diffusion tank.Measure of the two-dimensional concentration field using digital image processing technology was put forward on the base of vertical two-dimensional complex-tank from the vertex during the distribution experiment.A digital processing system for the experiment was builded by using Rhodamine B as tracing material.Distribution curve of concentration was better by homomorphic filtering,median filtering,color space conversion model and clustering segmentation algorithm processing.After these steps,the visualization of the tracer concentration gradient was realized,and the basic characteristic of the tracer diffusion in water transport was reflected.In this study we focused on three typical bank shapes commonly seen in rivers and reservoirs,including sloped step bank,sloped wavy bank and sloped wavy step bank.The objective was to study the concentration distribution of side discharge and its application.Our vertical 2-D sloped-bank diffusion tank and variable-frequency vibrating-grid system was employed in the experiments to simulate these banks in the situation that the lateral and vertical diffusion coefficients are different.Different compound scales for the compound part of the bank,different inclination angles ?=2?/?(corner field mapping coefficient ?=8,9,10,11…)for the sloped part,as well as various wavy shapes or step heights was studied to explore concentration distribution orderliness in complex bank side discharging situation,the changing pattern of lateral and vertical diffusion coefficients,the calculation method of the pollutant mixing zone's shape and characteristic parameters for variable-coefficient longitudinal flow.Experimental study found:(1)In the wave and straight sloped bank,when pollutants enter the water,the leteral diffusion coefficient is larger than the vertical diffusion coefficient.When the angles of wave bank was 30°and 45°,pollutants in the water surface were subordinated to half normal distribution.They were roughly the same as the corresponding angle of the theoretical concentration distribution.With the increase of angular field angle,compared with 30°,45°angle had obvious vortex.The scale of vortex was large and clockwise.The edge concentration of vortex was high while the central concentration of vortex was low.It changeed the concentration distribution of pollutants in the shore.In the experimental study,compared with sloped bank,we found that the lateral and vertical diffusion coefficient of wave bank were larger than the diffusion coefficient of sloped bank.With the increase of vibration frequency,the lateral and vertical diffusion coefficient also increased.Under the same vibration frequency,the lateral diffusion coefficient of pollution cloud were basically stable.(2)In the vertex emission experiment of the sloped wave ladder bank,the lateral diffusion of pollutants,along the surface of the water,was faster than the depth diffusion.Especially before the pollution cloud spreading to the central area,the lateral diffusion coefficient was greater than the vertical diffusion coefficient.When the lateral position of ladder was smaller,the lateral diffusion features of pollution cloud in the ladder became more obvious.With the increase of frequency,the development of pollution cloud accelerated in the lateral and vertical ladder.The ladder made a difference to the diffusion development of pollution cloud and the shape of pollution mixing zone.The results of this project will have great theoretical and practical value for revealing the regularity of its variation,dividing the side pollutant mixing zone in rivers and reservoirs,calculating the pollution capacity of water area,implementating the water pollution mixing zone permit system and improving water environment management level. |
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