Pulsed laser velocimetry measurements of the vortex shedding from structural elements

Previous work by the Authors demonstrated the existence of two shedding states for T-beams and L-beams. The Strouhal number was shown to change from 0.14 to 0.20 when the angle of approach of the wind altered by approximately 5° at certain angles. No complete explanation of this effect was available at the time. The present paper explores this bistability by intaanteneous flow field mapping using the pulsed laser velocimeter speckle velocimeter). The formation of the eddies is both visualised and measured using a 10 joule ruby laser. © 1989.