VORTEX-INDUCED VIBRATIONS AND WAKE STRUCTURES OF ISOLATED PLAIN AND STRAKED CYLINDERS MOUNTED ON A 2DOF ELASTIC BASE

摘要

This paper presents experimental results concerning the response of plain and stroked circular cylinders. The isolated cylinders are mounted in a two degrees of freedom elastic base. Two straked cylinders are tested and they have the same pitch p=10d and two different heights h-O.ld and h=0.2d. The longitudinal and transverse amplitude responses and wake structures of plain and helically straked cylinders are compared. The wake visualization uses the stereoscopic digital particle image velocimetry (SDPIV) technique. Comparing to the plain cylinder response, the p=10d and h=O.ld strakes moderately reduce the maximum amplitude response, while the p=JOd and h=0.2d strakes suppress the vortex-induced vibrations. The stroke effectiveness is directly related to the stroke height. The Reynolds number varies from 1000 up to 7500 in the experiments.