AN EXPERIMENTAL STUDY OF FLUCTUATING LIFT ON A SQUARE-SECTION CYLINDER OSCILLATING TRANSVERSELY IN A UNIFORM STREAM

Experiments on a square section cylinder fixed and forced to oscillate transversely in a uni-form stream were conducted in a water tank.The Reynolds numberof the experiments is in the range of 3·10~3tO 10~4,the amplitude to side length ratio A/D is up to 0.7 and the range of reduced velocity is4.5<Vr<12.This study aims at investigating the lock-in phenomenon,the fluctuating lift and the phaseshift between fluctuating lift and displacement of the oscillating cylinder.The problems on the aeroelastic insta.bility relating to present experimental results have been discussed.The flow visualization clearly shows thatthere are drastic changes of vortex-shedding from cylinder at the resonance point and the upper end of thelock-in range.The results of the flow visualization give better understanding of the physical mechanism of thephase shift.