Law Of Vertical Turbulent Mixing Of Pollutantin Natural River And Its Application

Law of Vertical Turbulent Mixing of Pollutant in Natural River and its Application(Ph.D. Dissertation) Doctoral Candidate: Du YanliangAdvise: Prof. Chu Junda Hohai University, Nanjing. P.R.CAbstractThe study of the turbulent mixing and transportation in the natural river is of theoretical and practical importance. Plenty of indoor and outdoor experiments, theoretical analysis and application research on this object have been performed, and have bought about a lot of results by many investigators. On the base of summarizing the results, the law of vertical turbulent mixing and transportation in the natural river is researched and applied in numerical model through the theoretical derivation combined with analysis of the data of measurement in this dissertation.First of all, the vertical mixing law of point source in the river is studied. By the theoretical derivation, the equation of the vertical homogeneous mixing distance of the continuous and instantaneous point source is developed. The definition of the part depth of homogeneous mixing is given, and its equation is obtained. These equations are verified by the measure data, such as the data of Nanjing section in Yangtse River, and the results are satisfied. In consideration of the influence of vertical mixing, the concentration field is calculated in the tentative channel. In comparison with the concentration field, which is calculated by traditional model, it is found that the effect of the vertical turbulent mixing on concentration field in the near field is large, while the effect in the far field is small. At the end of this chapter, the influence of the depth of discharge point on the concentration is analyzed.The vertical mixing law of the linear source in the natural river has been studied in the second step. At first the concentration equation of the linear source at different depth has derived. By the theoretical analysis, the relationship between the distance of the vertical homogeneous mixing and the part depth of homogeneous mixing, and the equation calculated distance of whole depth homogeneous mixing for the linear source have been presented. These equations are verified by the measure data in Nantong section in Yangtse River, and the results are satisfied.On the base of the vertical mixing law, the part depth homogeneous mixing 2D numerical model has been developed, and it was used in the concentration field calculation. By use of the measure data of Rbodemine-B tracer in Yangtse river estuary, the comparison of value calculated with data measured has been made. The value calculated by the new model approximates the measure data, and the value that calculated by the whole depth mixing 2D model is much less than the measure data in the near field. This model is also superior to the traditional 2D model for its precision. The new model saves lots of time and resource of computer and has more facilitation when it compares with the 3D numerical model.In the tidal estuary, the current is complex, and the flow is oscillatory. Some experiential formulation has presented to calculate the vertical turbulent mixing coefficient. On the base of analysis of the hydrodynamic in the estuary, the theoretical equation, which describes the distribution of the space and time of vertical turbulent exchange coefficient, has developed, the equation has applied to the practice.To analyze the hydrodynamic structure of the estuary, 3D K- numerical model with curvilinear fitted coordinate has developed. The distribution of velocity and turbulent exchange coefficient at different time has obtained and analyzed. The concentration field calculated by the 3D numerical model approximate to that calculated by the partial depth homogeneous mixing 2D numerical model.