Computer Numerical Modeling Of Sedimentation Tanks

Based on hypothesis of ideal sedimentation tanks which has been provided by hazen and camp, and by referring to many domestic and foreign literature , the hypothesis of ideal sedimentation tanks were analyzed and discussed in the thesis, points out that the hypothesis does not quite accord with practicality sedimentation tanks o In fact, a lot of factors would affect on the flow field and concentration field of sedimentation tanks ccording to laminar flow hypothesis, governing equations were established with vorticiy-stream function method which are deformation of Navier-Stokes equations. Programs were compiled with numerical modeling of the finite difference method and mix finite analytic method. The flow fields in several sedimentation tanks were simulated with the programs. The results showed that the hypothesis of ideal sedimentation tanks does not quite accord with practicality sedimentation tanks even in the condition of laminar flow hypothesis. In effect, the flow types in horizontal flow tank, vertical flow tank and circular flow tank, all are turbulence flow. Based on this fact , the sedimentation law of suspension was analyzed and discussed, by introducing the theory of multiphase eulerian model in fiuent6.0 edition which is a general , greatness computation software which were abroad used in computing and analyzing the flow field and heat transfer etc. The flow field and concentration field in horizontal flow tank , also the flow field of vertical flow tank and circular flow tank were simulated and analyzed comprehensively by using the multiphase eulerian model. The results showed that the flow field had great different in vertical flow tank or circular flow tank with ideal sedimentation tanks. When sedimentation tanks were designed according to the hypothesis of ideal sedimentation tanks, one would depend greatly on empiricism, subjectivity and arbitrariness.Finally , some conclusion can be summarized. (1)Practicality sedimentation tanks show great different with ideal sedimentation tanks;(2)Second, the flow field of sedimentation tanks should be simulated in turbulence flow model; (3)The location and length of baffle, the design of mud-container have some effect on the flow field and concentration field in sedimentation tanks; and (4)The density and dimension ofsuspension granule included the flux magnitude in sedimentation tanks inlet are the important parameters for determining settling efficiency of sedimentation tanks. In addition , some good suggestions and idea were given in this paper , They would provide fully evidence for understanding the flow field and movement law of suspension granule in sedimentation tanks, for optimizing design of sedimentation tanks, for achieving the unification between the engineering-economy with the society-benefit. The results abtained in the thesis have great theory meaning, practicality meaning and engineering meaning.Guo shengchang (Environmental Engineering) Supervised by Professor Chen Liang and Professor Chen Dong Hui...