| Nowadays, the spillway tunnel with a concave curve which connected the inlet and the main body, is a mature, usually-seen type when an alteration of a diversion tunnel to a reused permanent tunnel is carried out. The engineering-related spillway tunnel in the hydropower plant is in the upstream. Based on the fundamental theory and methods in the turbulence and the two-phase flow numerical simulation, this thesis uses the basic principles of the flood energy dissipation to model the flow and the aerated flow in the spillway tunnel. Appropriate computational models for both laminar and turbulent flow are chosen to carry out the simulation and the analysis results are given.To summarize, the main work done in this thesis are the following content:(1) Model the large flow of spillway tunnel.With a engineering example, it gives a computational model using the basic theory in laminar flow, turbulent flow and the water-air two-phase flow, and then the analysis and the contrast of the flow patterns, the velocities and the pressure of the large flow are given.(2) Model the aerated flow after making the aeration tank in the anti-arc section part of the spillway tunnel.From the study in (1), make the aeration tank at the both ends in the anti-arc section part, where the negative pressure is huge, the velocity is high and cavitation is easy to happen. The contrast between (1) and (2) are given.Results:(1) With the guidance of the tutor and the expert in related field, it looks up the specification and the books to search for the blueprints of the spillway tunnel. For the flow-air in whole tunnel about550m long, it establishes a geometry model to realize the simulation and the analysis.(2) I proposed a calculation method which made laminar model of fluid flow to full the whole tunnel,in the size very large of geometry model and calculation complex working conditions, utilize laminar and turbulent model to calculate, then results of laminar and turbulent were compared and showed difference in the moment-curvature relationships,but the laminar method can improve work efficiency.(3) To simulate the fluid flow.Obtian a results,beginning of the flip bucket roof existing the largest negative pressure,and in the root of bucket-end be larger pressure also.And the obvious negative pressure, the low pressure area and mixed gas pressure gradient and blind area a drastic change area appeared in the tunnel.(4) Adding aeration slot on the flip bucket’s beginning and end to make the air work in water, and ensuring the flow and other related water conditions remain unchanged. We found mixed with gas, the biggest negative pressure, the low pressure area and mixed gas pressure gradient and blind area eased in the flip bucket.Considering the grid will influence degree of computational results, to detailed design and tried to repeatedly calculate each simulation object’s mesh are divided in this paper.With pressure index judgment grid arrangement and degree of whether can meet the engineering degree in need, to ensure the reliability of the results.The aerification mitigation cavitation and flood energy dissipation is a multidisciplinary problems, which is very complex problem and involve many elements and the problem is very complex.In the subsequent research project,what is puting to use theoretical analysis, numerical simulation,experimental analysis, prototype observation and so on methods of combining.These are very necessary in-depth study. |
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