| Due to efficient energy dissipation and cost savings, the integrative energy dissipater including flaring gate pier, stepped spillway and stilling basin (IED) has been widely used in flood discharge structures with large flow and high head flood. But it is found in actual engineering practice that cavitation phenomenon is easy to occur in front steps of stepped spillway. Cavitation bubbles move along the flow and rupture in downstream high pressure area which could result in cavitation damage in solid wall surfaces.Based on the X power station, RNG k-ε turbulence model and two-phase of the water vapor VOF model, geometry reconstruction for interpolation, PISO and unsteady algorithm were utilized in this paper to numerically simulate the three-dimensional flow field of the integrative energy dissipater in different aerator and head step size, and through the model experiment to verify the reliability of numerical simulation. The main research results are as follows:1. Influences of the aerator angle and height on hydraulic characteristics of the stepped spillway(1) Along the flow directon, the distribution trend of computing water depth and pressure of each program with different aerator sizes is consistent.(2) When other factors are certain, the air concentration of decreases in general with some fluctuations on the vertical and horizontal face of steps but it stays unchanged at the end of a few steps. The starting position of negative pressure of each program is slightly different. There is a jump zone of absolute value of negative pressure in each program which is caused by air concentration mutation. The cavity length, the absolute value of the maximum cavity negative pressure and air concentration increases with the augment of the aerator angle. The absolute value of the maximum cavity negative pressure increases with the enlargement of the aerator height but the cavity length and air concentration decreases with augment of the aerator height.(3) The bottom velocity of each program gradually decreases along the flow direction. The rate of energy dissipation gradually increases along the flow direction, which increases faster in the front of the stilling basin and smaller in the end of bank nearby. When other factors are definite, the bottom velocity at the same dection decreases and the rate of the energy dissipation increases with the enlargement of aerator angle or the reduction of aerator height.2. Impacts of the first step height and mesa angle on hydraulic characteristics on stepped spillway(1) The distribution trend of the computing water depths and pressure of each program with different first step heights and mesa angles is agreement.(2) When other factors are assured, the air concentration and the trend of negative pressure on horizontal and vertical face of steps are coincident with they are in different aerator shapes. There is a negative pressure jump zone which is caused by air concentration mutation. With the augment of the first step height, the absolute values of the maximum cavity negative pressure decreases, and the cavity length and concentration increases. With the mesa angle of the first step face expands, the cavity length and air concentration decreases; and the absolute values of the maximum cavity negative pressure increases.(3) The bottom velocity of each program gradually decreases along the flow direction. The rate of energy dissipation gradually increases along the flow direction, which increases faster in the front of the stilling basin and smaller in the end of bank nearby. When other factors are certain, the bottom velocity at the same section reduces and the rate of energy dissipation increases with the increasement of the first step height. The bottom velocity reduces and the rate of energy dissipation increases with the reduction of the first step mesa angle.Comprehensive analysis indicated that the transition connection mode of the aerator angle 11.3°, height 1m and the first step height 2m is better. |
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