Color schlieren deflectometry study of jet mixing: effect of buoyancy and perforation

Mixing of jets is crucial for optimal performance of many industrial applications and there is a need to optimize both nozzle geometry and flow conditions. The present study reports the influence of buoyancy and perforation on mixing between a jet and its environment. Optical techniques are ideal for the study of jet mixing due to their non-intrusive and inertia free properties. The present study gives an account of mixing between helium jet and the ambient fluid using a combination of color schlieren deflectometry and radial tomographic mathematics. Four different perforation sizes have been used and the experiments are performed for Reynolds numbers 21–676 and Richardson numbers 3.27–0.0015. Color schlieren images show distinct influence of perforation and flow conditions (Richardson number). Oxygen concentration and jet width quantify effectiveness of jet mixing. Buoyancy plays an important role in mixing at high Richardson number. Perforation improves jet mixing i.e. there is about 120% increase in jet width and the size of perforation plays an important role.