Flow induced vibration in square cylinder of various angles of attack

Abstract

An experimental study was carried out to identify the effect of angle of attack on flow-induced vibration (FIV) of square cylinders. The experiment was conducted at the Aeronautical and Wind Engineering Laboratory (AEROLAB), UTM Kuala Lumpur using a wind tunnel that was free from external wind conditions. A supporting structure was designed and fabricated to conduct this experiment. The importance of this support structure was to enable the rigid cylinder to suspend and vibrate freely upon excitation of wind speed. The results were analysed through the response of amplitude and frequency of the rigid cylinder over a velocity range of 0.5m/s to 4.0m/s. The results showed that for a square cylinder of a=0°, vortex-induced vibration (VIV) occurred at low reduced velocity (UR) in range of 5 = UR = 10 and galloping occurred at higher reduced velocity which started at UR=15. A tranquil zone was found between VIV and galloping in the reduced velocity range of 10 = UR = 15. As for a=22.5° and 45°, only VIV response was found at low reduced velocity in range of 4= UR = 9.