An investigation of the effect of tabs on jets using advanced diagnostics

The effect of tabs on supersonic jets has been assessed using two laser-based experimental techniques. In the first instance, visualizations of the mixing layer were obtained simultaneously from two orthogonal vantage points, yielding considerable insight into the characteristics of the mixing. Secondly, quantitative data was gathered using filtered Rayleigh scattering (FRS). Instantaneous images were collected for both techniques using a Nd:YAG pulsed laser and intensified CCD cameras. Average streamwise velocities were measured in isothermal Mach 1.0, 1.5, and 2.0 jets using FRS across the two-dimensional image field. When tabs were employed, the molecular scattering clearly showed the drastic deformation of the jet. From these images, quantitative data was derived which definitively identifies the presence of counter-rotating streamwise vortices generated by each tab.