Lagrangian Schlieren Image Velocimetry Measurements in Exhaust Plume

Schlieren image velocimetry (SIV) is a non-intrusive flow visualization technique. SIV is the combination of schlieren optics and image processing methods to simultaneously characterize and measure the velocity fields of naturally occurring turbulent flow features. The focus of this work was image processing methods for SIV analysis. Image processing methods were explored with MATLAB to enhance the appearance of the turbulent flow features to convert them into optical particles. The optical particles were individually identified to determine their characteristics for subsequent tracking to measure velocities. With known parameters such as size, location, and centroid, filters were applied to isolate specified particles. Manual SIV was performed due to the limitations in an automated pattern recognition script to construct a path from the optical particles.;Here the SIV technique is applied to a free jet, a micro-turbine, and a small-scale liquid rocket engine to construct a velocity distribution in the exhaust plumes at various locations from the exit plane. Velocity distributions in the testbeds revealed similar trends to those of published data for free jets. Experimental results were limited to the lower velocity turbulent regions because SIV is only valid where the optical particles are present and visible in schlieren images.