Abstract
The purpose of the paper is to investigate the characteristics of the unsteady aerodynamic forces acting on a three dimensional square prism which is sinusoidally oscillated across wind direction with a rocking mode. Wind tunnel experiments were conducted by use of the forced oscillation technique suggested by Bishop and Hassan. The following results were obtained. 1) The unsteady aerodynamic forces acting on an oscillating model showed the non-linear phenomenon with respect to the reduced wind velocity and the oscillating amplitude. 2) The application of the quasi-steady theory to the galloping oscillation is thought to be difficult below the reduced wind velocity of 30. 3) The existence of the locking-in region is observed. The region is expanded according to the increasing wind velocity. 4) The response curves related to the oscillating amplitude and the wind velocity are obtained, which are plotted with the parameters of the mass damping ratios. 5) The experiments by the forced oscillation technique are compared with the free oscillation experiments. The good agreements are observed with the both results.
