Experimental Investigations of Vortex Induced Vibration of A Flat Plate in Pitch Oscillation

A bluff structure placed in a flowing fluid, may be subjected to vortex-induced vibrations (VIV). For a flat plate with only rotational degree of freedom, the VIV is rotational oscillation. Based on the experimental investigation, vortex-induced oscillation of the plate is studied. The Strouhal number is measured from the stationary plate in a low speed steady wind tunnel. A set of vibration tests are conducted to investigate the relationships between shedding frequency and vibration frequency. ?lock-in? phenomena is observed with and without large amplitude. An empiricalanalytical model via introducing a nonlinear van der Pol oscillator is developed. This thesis investigates the ?lock-in? phenomena of a flat plate in pitch oscillation. Results from wind tunnel experiments on a flat plate indicate the ?lock-in? is frequency ?lock-in?, resonance which appears large response amplitude occurs in the ?lock-in? regime and may be influenced by ?lock-in? phenomena.