Vibration of a semi-rigid cantilever in a cylinder’s unsteady wake at zero incidence angle

Abstract

We present an experimental study of the dynamics of semi-rigid cantilevers in a cylinder’s wake using a vertical soap film tunnel. Experiments were conducted using cantilevers of two rigidity moduli 2.7×10−8 and 6.5×10−8 Pa-m4 with two lengths 7.5 and 15 mm. Cantilevers at zero inclination angle (free end pointed downstream) were placed downstream of a cylinder with radii values ranging from 10%–120% of the cantilever lengths. The study was conducted for three downstream gap distances 10 mm, 25 mm, 40 mm, measured from the cylinder’s trailing edge to the cantilever’s fixed-leading edge. The Reynolds numbers were, 4500<ReD<25000 and 14000<ReL<40000 based on cylinder diameter and cantilever length, respectively. The cantilever motion and wake vortex structure were visualized and analyzed to estimate vibrational amplitudes, frequencies, local phase angles and vortex shedding frequency. The cantilever vibration and vortex shedding results indicated possible flutter phenomena (vibration at the cantilever’s natural frequency) as well as vortex induced vibrations (VIV).