Development of a High-Speed Three-Dimensional Flow Visualization Technique

A high-speed three-dimensional Now visualization system has been developed and is described. The technique is based on the high-speed scanning and subsequent imaging of a two-dimensional laser sheet through the flowfield. A three-dimensional image is then reconstructed from the stack of two-dimensional slices. The technique achieves high speeds using a home-built megahertz-rate pulse-burst laser system, a galvanometric scanning mirror, and a highspeed intensified charge-coupled-device camera capable of 500,000 frames per second. These components allow for the acquisition of three-dimensional image data with a resolution of 220 x 220 x 68 volumetric elements (voxels) in 136 mu s. The speed of the technique is limited by the available camera speed and can be increased substantially using a higher-speed camera. The technique is demonstrated through three-dimensional visualization a turbulent round jet (Re = 6700) seeded with small water droplets for light scattering. Three-dimensional flow visualization images display numerous three-dimensional features of the jet, including ring vortices, azimuthal modes and counter-rotating streamwise vortex pairs. Future work will focus on the development of a high-speed three-dimensional laser-induced fluorescence technique.