3-D Numerical Simulation And Analysis On Energy Dissipation Of Multiple Jets For Pipe Outlet

The submerged discharge sleeve valve with multiple jets is served as a new type of energy dissipater for pressure pipe, by which fluid energy of pipe outlet can be dissipated through entrainment and mixing of the high speed flow shot out from the multiple jets at multilevel into the plunge pool, in which strong turbulent flow can be produced. At present, the researches on pipeline with multiple jets mainly concentrate on the blending problem in power engineering and the physical diffusion problem in environmental engineering. Whereas few researches on using turbulence of multiple jets to dissipate the dump energy of pipeline outlet are made. The RNG k - e model is applied to simulate the 3-D flow field on energy dissipation of multiple jets for pipe outlet in this paper. The sizes, quantity and layout of the nozzles effecting on energy dissipation ratio are studied, and the optimized layout of the nozzles is explored primarily.Firstly, the jet theories are reviewed from various aspects and different mathematical modeling technologies of turbulent flow are analyzed and evaluated. It is preliminary for the establishment and improvement of the model in the thesis. An appropriate mathematical model of multiple jets is established by comparing advantages and shortcomings of different models based on actual conditions. The flow control equations are given, and closed, discretized and numerically solved.Secondly, the single jet and double jets are simulated and at the same time the mechanism of jets is researched. The calculation of numerical simulation is verified in accordance with the experiment data, and the results shows that the calculated value is consistent with the experimental value. It follows that the mathematic model adopted is reliable and the analog computation is reasonable.Energy dissipation of pipe outlet of the Yellow River Diversion Project was a practical example. The effect of the flow field for the plunge pool about adopting the VOF method or the elastic-lid method to simulate the free fluid surface are compared, which shows that there was a small discrepancy in the result of two methods, especially there was no influence on flow field. So imitating free surface with the elastic-lid method is feasible. The result is analyzed and shows that the energy dissipation ratio depends on the sizes, quantity and layout of the nozzles. In order to compare the energy dissipation effect of different cases, the concept of remained energy ratio is presented, by which the energy dissipation ratios among many cases are compared. And it can be found that the energy dissipation effect in the staggered arrange of holes is better than in the parallel arrange, and the relation curve has been obtained about the remained energy ratio and the numbers of nozzles. According to Simulation results, it's found that more nozzles are better for the energy dissipation effect under the existing area of nozzles and entry conditions while the variation slows down obviously as the number of nozzle increases to a certain number, so the attenuation of energy can be achieved without increasing nozzles.