چكيده به لاتين
Dams consist of different structures each of them need proper hydraulic design. A proper design is essential to know flow around these structures. Improper design of these structures causes cavitation and separation of flow, especially at entrance of these structures. For emergency situations in operation of dams, spillways performance is considerated. Symmetric flow without disturbance at entrance of spillways provides better performance, and increases spillways efficiency. Due to the curvature of approach flow, designers have to design guide walls in front of spillways. Guide walls geometry plays an important role in decreasing vortices and creating a uniform approach flow.
In this study, flow behavior through Jareh spillway was simulated by using Flow 3D software, and the results of numerical simulation was validated with experimental data. Then, using numerical simulation, evaluation of the effect of guide walls geometry on conditions of approach flow as well as performance of spillways was done. The results showed that the vertical inclination of guide walls and piers is the main affecting factor in approach flow condition through spillways. In this study, increasing 44% of vertical inclination of left guide wall resulted in turbulence energy reduction to 43% and discharge coefficient of spillway rise to 12.9%. Increasing 28% of vertical inclination of piers on spillway, flow behavior became more uniform, and discharge coefficient increased up to 11.06%. Results showed that optimal values of both the straight length and horizontal inclination of guide wall is affected by topography of approach channel, the angle between axis of approach channel, and spillway. In general, increasing straight length of guide wall, leads to reduction of average velocity and turbulence energy in approach channel. In this work, optimal value of this length increased discharge coefficient to 4%.
Keywords: spillway, guide wall, flow pattern, discharge coefficient, Flow 3D.
