Experimental investigation on the VIV-galloping instability of a 3:2 rectangular cylinder

The interaction between vortex-induced vibration and galloping for an infinitely long 3:2 rectangular cylinder was investigated through wind tunnel tests. This section was found to be very unstable and large vibration amplitudes were observed also at high Scruton number due to this interference effect. In order such a phenomenon not to occur it was necessary to increase significantly the mass-damping parameter. In particular, no interaction was observed for a ratio of the quasi-steady galloping to vortex-induced vibration critical wind speeds as high as 7.5, while it was still present for a ratio of 5.3. The practical consequence of that seems to be the necessity to install dampers in several prismatic slender structures with a rectangular cross section similar to the one considered herein.