Experimental Study of Flow-Induced Vibrations on Vertical Gate with Underflow

ROMAGNOLI, M.; ENDRES, L. A. M.

Ciudad Guyana

Congreso; III INTERNATIONAL SYMPOSIUM ON HYDRAULIC STRUCTURES; 2006

IAHR

An experimental investigation of flow-induced vibrations on vertical gates with underflow is presented. The purpose of this study is to investigate the characteristics of flow-induced vibrations on an elastic device representing a vertical under flown gate with different gate bottom lip shapes. The elastic device which consists of an aluminum flat plate with approximate dimensions of 500 mm of width x 800 mm of height x 20 mm of thickness, is allowed to oscillate in streamwise direction. Five different gate bottom lips in contact with the flow in gate opening values of 10, 20, 30 and 40 mm are investigated. Behaviour of vibrations of the device is characterized by measurements of instantaneous acceleration in the streamwise direction and average water levels around the flat plate. Rectangular (20 and 10 mm thick) and with 30° bevel at the upstream face bottom lips geometries have proved to be more prone to flow-induced vibrations, with differences up to 3 to 4 times in the dimensionless root mean square values of acceleration in comparison with the variants with a 60° bevel at the upstream face and of 30° at the downstream face. The frequency of flow-induced vibration in the respective openings and bottom lip shapes varies, approximately, between 1.10 and 0.90 of the value of the natural frequency in air. Hence, the influence of the added mass on the vibrating gate does not seem to be very significant.