Field and laboratory cavitation studies of the sluice at the Bukhtarma hydroelectric power plant

Abstract

1. The results of field and model spillway cavitation studies at the Bukhtarma hydroelectric power plant indicate that a reliable prediction of spillway cavitation phenomena is possible only with the use of vacuum-cavitation tunnels. The prediction of cavitation phenomena by testing models in an open hydraulic arrangement, i.e., without modelling the pressure on the free surface of the stream, may lead to a significant reduction in the actual vacuum, and in the long run, to underestimation of cavitation risks. 2. Analysis of the cavitation and hydrodynamic flow characteristics in the field and on the model provides the basis for us to assume that with Reynolds numbers of the order of 105 and above, a condition of Reynolds self-similarity is observed in modeling cavitation at hydraulic intake structures. The effect of factors that cannot be modeled (air saturation, the chemical composition of the water, the presence of impurities insoluble in water, etc.) on the prediction of cavitation phenomena with the use of vacuum stands is negligible. 3. The cavitation process both in the field and on the model is accompanied by highfrequency pressure pulsations. In testing models of structures in a vacuum stand, the amplitude characteristics of these pulsations are modelled according to Froude numbers under conditions where the external pressure above the free surface of the stream is modelled in a stand. The frequency spectra of the high-frequency component of pressure pulsations with cavitation are virtually coincident in the field and on the model. 4. The studies indicated that the Bukhtarma hydroelectric plant spillway has an insatsifactory profile, which significantly deforms the stream and produces cavitation. It is possible to prevent this by varying the profile of the springboard surface and, primarily, the lateral walls.