Hydraulic calculation of free-flow eddy spillways

Conclusions

• 1. The calculation method presented pertains to free-flow eddy spillways, where the regulating gates (vertical-lift or radial) operate in normal undrowned regimes with a free flow in the gate chamber. This is provided by the appropriate selection of the dimensions of the gate and swirl chamber in accordance with Fig. 2a, which makes it possible to design gate equipment without additional investigations of its operating conditions.

• 2. The developed method of theoretical analysis and prediction of the characteristics and operating conditions of free-flow eddy spillways is based on conservation laws and takes into account the size and shape of the waterway, hydraulic losses of energy in the influent conduits, regulating gates, and due to wall friction. The derived analytical formulas and relations enable calculating the geometric parameters of the spillways, flow regime, and characteristics of the flow in them in conformity with given values of the head and discharge.

• 3. The calculations confirm that in free-flow eddy spillways the excess kinetic energy of the discharge is effectively dissipated due to an increase of hydraulic losses during swirling of the flow along the length of the outlet conduit.

• 4. The calculations agree well with the experimental data. Consequently, the calculation can be recommended for practical use when designing. Nevertheless, it does not eliminate the need for laboratory hydraulic investigations of the selected design variant of the free-flow eddy spillway, just as one cannot do without laboratory investigations of spillways of the usual types, despite the fact that methods of calculating the latter are sufficiently detailed and accurate as a consequence of the more than 100-yr experience in their design, investigation, construction, and operation.