Measurement of Coupled-Mode Instability on Model Scale: Details of Validation

Abstract

Experimental validation of the proposed mechanism of self-excited coupled-mode instability of Tainter gates, developed in Chapter 10, was obtained using laboratory models of Tainter gates. Results from both two- and three-dimensional model testing are reported. In the two-dimensional section model, the skinplate was simulated by a spring-mounted plate with the same upstream shape as the Folsom Dam gate. The simulated skinplate could undergo streamwise rotational vibration about its attachment point on the radial arm structure. The radial arm structure was also spring-mounted and could under torsional vibration about the trunnion center. The 1/13-scale three-dimensional model was carefully designed to maintain an in-water natural vibration frequency close to the same value as for the prototype Tainter gate with a similar bending mode shape to that of the Folsom gate. Both sets of model tests confirm the predictions from the theoretical development in Chapter 10.