Schlieren interferometry in the mass diffusion of a two-dimensional jet

Objective of this work was to show that schlieren interferometry is a useful quantitative technique to study mass diffusion processes of binary gas mixtures and in particular to apply it to investigate the initial region of a two-dimensional helium jet mixing with air. For low Reynolds number (Re) helium mole fraction at the nozzle exit was lower than unity, and the jet initial region was absent. The latter was recovered at higher Re and the potential core length increased for increasing Re. Strong mole fraction gradients beside the nozzle lips were found for a distance of about one nozzle width.