Sayano-Shushenskaya catastrophe — synchronous hydroacoustic resonance?

Two models are considered for propagation of acoustic waves in the water conduits of Francis turbines at hydroelectric power plants (HPP). Transfer functions are cited for a dynamic “pressure-conduit/turbine/draft-tube” system during a pressure disturbance beyond the turbine. Fulfillment of the Nyquist criterion for the above-mentioned system indicates its stability at any openings of the final-control element. Analysis of analytical relationships between frequency characteristics and parameters characterizing the wave properties of sections of the water conduit makes it possible to isolate frequency regions in which manifestation of resonance is possible, and also evaluate its amplitude. The frequency response of the water conduit at the Sayano-Shushenskaya HPP, for which three resonances are isolated in the ultra-low acoustic region is given in the conclusion. A mathematical model of the process is developed and investigated. Oscillograms of pressure pulsation during pressure disturbances in the final third of the draft tube are presented. Results of the investigation are compared with published data derived from full-scale tests.