Author(s): Jalal Attari
Linked Author(s): Jalal Attari
Keywords: Hydraulic structures; Gates; Seals; Pressure fluctuations; Shearlayers; Flow-induced vibrations
Abstract: Gates are widely used in hydraulic structures for regulating discharge and water level. An important in design of any type of gate is an effective seal to prevent leakage of water. It is known that elastic seals, especially of J-type, are susceptible to vibration at small gate openings. In the present study, a bar type bottom seal for a submerged radial gate is considered at very large gate openings from the standpoint of excitation of flow induced-vibration. Instead of a water channel, pressure fluctuations were measured on the bottom seal of a stationary model radial gate mounted in a wind tunnel. Power spectra of the pressure fluctuations showed some broad band peaks. Strouhal numbers were deduced using these frequencies and previously measured maximum shear layer velocities. Results show good agreement with the theoretical and experimental results of Martin et al. (1975) for a vertical gate with extended lip. Furthermore in the present experiments, results have been extended to a 3`rd mode of oscillation. Comparison of results shows a strong similarity of local flow processes between the gate with a protruding bottom seal and those with an extended lip despite their differing global geometry. This suggests that an instability-induced excitation with fluid-dynamic feed back is the governing mechanism.
Year: 2001