Seite - 1565 - in Book of Full Papers - Symposium Hydro Engineering

the nappe forms, and experimentally investigated the behavior of the flow choking. The estimated formulas for nappe maximum width and its location of slit-type flip buckets were presented by Liu et al. Huang et al. developed a method to calculate the dynamic water pressure in the contraction section of STED. Ippen (1943) put forward the ideal shock wave theory based on the mechanical principle, proposed the basic equations of shock wave, then the main theoretical foundation of the contraction type energy dissipaters was laid. Ippen’s formulas was then simplified by Hager et al. (1987) and Liu et al. (1999) Ippen’s theory following several assumptions: (1) the deflection angle of flow is small; (2) the friction of side wall is negligible; (3) the pressure distribution along the depth of the water conforms to the hydrostatic pressure distribution regularity. However, the flow regime in the STED no longer satisfies the assumptions, for the rather sharp deflection angle, and the narrow width of the surface. So Ippen’s formulas would result in large deviation, and need to be modified for the application in STED. As a special hydraulic phenomenon, the water wing caused by the shock waves in the contraction section of STED may bring about harmfulness to the stability of the bank and the safety of the downstream buildings. However, the harmful effects caused by water wings has been hardly attached enough importance. In hydraulics prototype observation of Geheyan project, it was found that, the water wing caused by the STED diffused transversely, scoured the side bank slope. And the operation of the upper outlet on both side was then limited. The results of model test of Shiubuya project confirmed that, part of the water detached from the main flow from side outlet, and scoured the river bank. Hence it is necessary to carry out special study on the formation mechanism and movement features of the shock waves and the water wings. In the present study, physical model experiments and theoretical analysis were conducted to reveal the internal relation of the shock wave and the movement characteristics of the water wing. And then the estimation formula for calculating the shockwave - water wings spread area was proposed, based on the experimental data combined with theoretical derivation. 2. EXPERIMENTAL SET-UP AND METHODOLOGY The experiment model consisted of a water tank, a sloping flume, a STED structure, and a downstream pool, as shown in Figure 1. The high pressure water tank is 10 meters high and provided adequate flow with enough water head. The flow was delivered by a Plexiglas-made sloping flume into the STED structure. The sloping flume is 3.2 m long, 0.2 m wide and 2 m high. A radial gate was set near the downstream end of the flume to adjust the Froude number of the flow in the STED contraction section. The main geometric parameters of a STED are the length of the contraction section L, the bucket angels α, and the widths before and after the contraction section B and b, as shown in Figure 1. Then, b/B is the contraction ratio. 1565