Aerodynamic Drag of Streamers and Flags

Low speed drag and flutter measurements of rectangular flags and streamers are presented. The streamers have aspect-ratios between 10 and 30; the flag has an aspect-ratio 3.3. Experiments are performed with three fabrics of different weight, bending rigidity and hysteresis. The streamers are fixed to a three-component force balance using two methods: by clamping of the luff on the support, and by a wire connecting luff and support. The parametric space studied includes wind speed, aspect-ratio, planform area, clamping method and fabric properties. Semi-empirical correlations for the time-averaged drag coefficient as a function of aspect-ratio are derived for cotton streamers. Flutter analysis shows that the oscillation of the streamers is complex, due to the effects of gravity and the turbulence created by the large amplitude oscillations. Power spectra density data are presented for some relevant cases.