Dynamic behavior of variable‐density, turbulent jets in their near development fields

Four round turbulent jets of hydrogen–nitrogen mixtures (initial density ratio ranging from 0.07 to 1) discharging into a slow air coflow are experimentally and analytically studied. The investigation is restricted to the near development field over which both buoyancy and coflow effects have negligible influence on the jet expansion. Two‐color laser Doppler anemometry provides the mean and fluctuation of the velocity components, while a laser Mie scattering technique with conditional seeding provides the radial profiles of mean density. Self‐similar behavior is investigated by using a local effective jet diameter that accounts for the strong density variations in the near development field. This scaling based on momentum flux conservation appears to be efficient for collapsing the centerline velocity data (mean and RMS) along a unique self‐similar curve for all jets.