Experimental Investigation And Numerical Simulation On Flow Pattern Of Horizontal Sedimentation Tank

With the development of society and economy and the improvement of quality of life , the shortage and pollution of water resources has been becoming an urgent issue to the human beings on the Earth . One of the important ways to deal with this problem is to build water treatment projects. Sedimentation is a very important process in the water treatment project, and a large number of suspended solids can be removed in this process. In a way, the effectiveness of the whole project is influenced by the effect of sedimentation, the whole process will be influenced by the effect of sedimentation. This paper studied with the model experiment and the numerical simulation method has given the flow pattern of the rectangular settling tanks in the water plant.The settling tank had been studied with the theoretical analysis and the numerical simulation method by most of the predecessor, but very few used the experimental study. In this paper, the similarity theory was introduced into the experimental study of the settling tank, then a physical model was made and an experimental system of the settling tank was build, and the PIV technology was used to measure two-dimensional flow velocity distribution in the physical model. Some conclusions are drawn from the result of the tests:(1) In the settling tank, flow field cannot simply be regarded as the turbulent or the laminar, but it should be divided into the inlet region, the settlement region and the outlet region, the fluid pattern of each group is different, and each group also has the different influence to the sedimentation of the suspended substance. (2) There are two dead-zones of water current in the settling tank entrance and the export. (3) In the settling tank, the basic reason of forming turbulent is the uneven water distribution. This article also puts forward some proposals to the settling tank design and the operation from the conclusion of the tests.In this paper, based on the analysis and summarization of study results on settling tanks by predecessors, a mathematical model for predicting the velocity distribution in rectangular sedimentation tanks is developed. Using SIMPLE algorithm for a non-orthogonal collocated grids variable arrangement, the variables can be solved with the CFD software. Then, the current field is finally simulated. Some conclusions are drawn by comparing with the experimental result. The simulation result is roughly consistent with the test result. The numerical simulation can replace the experimental study in the certain degree, but still has to increase the precision.