Laser Doppler velocimeter measurements on supersonic mixing nozzles that employ gas-trips

A cold flow laser Doppler velocimeter study was performed in the mixing region of supersonic mixing nozzles that employed gas-trips for enhanced mixing; the nozzles were operated with room-temperature nitrogen under simulated laser flow conditions. A determination was made of three mean and turbulent velocity components, in addition to two turbulent shear stress elements, under both trip-on and trip-off operation. To preclude velocity biasing, the primary, secondary, and trip streams were simultaneously seeded with 0.357-micron-diam. latex spheres. The objectives of this activity were to acquire basic cold flow information on trip nozzles in order to help develop some insight into the tripped mixing phenomenon and to acquire information that could be correlated with sophisticated computer models of the mixing process. The velocimeter results appear to support observations that were made earlier during a related laser-induced fluorescence visualization study.