The influence of flexible tabs on high speed jet noise

Flexible tabs have been shown to be effective for noise reduction in a number of low speed aerodynamic appli-cations, including aerofoils, and cylindrical bluff bodies, both square and circular. Although regular, non-flexible tabs have been investigated for the control of high speed jet noise, the application of flexible tabs does not appear to have been investigated previously. Therefore, the influence of flexible tabs on the noise produced by high speed jets issuing from circular nozzles was experimentally investigated. Single microphone measurements of the noise from air jets at flow speeds of Mach 0.8 and 1 with 3 different configuration flexible nozzles were obtained for a range of observation angles from 90 to 150 degrees from the jet axis. These results are presented as spectra and overall sound pressure levels. For the configurations of flexible tab nozzles and observation angles investigated the flexible tabs were found to increases overall sound pressure levels in all cases.Jesse Coombs, Tyler Schembri and Anthony Zande