Abstract
An experimental investigation of flow-induced vibrations of gates with multiple degrees of freedom is presented. An underflown vertical gate plate with submerged discharge was allowed to oscillate both in the cross-flow (z -) and in the streamwise (x -) direction. The two purposes of the investigation were to further the insight into the hydrodynamic coupling mechanisms of the two vibration modes and to determine the interaction of the unsteady lift and drag forces. Self-excited vibration tests were run with reduced velocities VrzandVrx from 0·8 to 14, covering a range in which the instability-induced excitation (IIE) due to impinging-leading-edge vortices (ILEV) as well as the transition to galloping (MIE) occurred. The ratio of the natural frequencies of the two vibration modes fx 0/fz 0, the gate opening ratios /d, and the submergence of the gate plate were varied. Depending on the ranges of reduced velocities and frequency ratios, a complex interaction of two different kinds of instability-induced excitation was detected. Furthermore, it was found that streamwise IIE-excitation and cross-flow galloping coexist. To assess the relevant fluid dynamic amplification and attenuation mechanisms, simultaneous body response and flow velocity measurements were carried out.
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