Turbulent Mixing of Gases with Different Densities

Abstract

Concentration and velocity measurements are carried out in a turbulent region of axisymmetric jets of H₂, He, Ar, CO₂ and air with quiescent air. The spreading angles of concentrations and velocities are larger for the lighter issuing gases. Though the decreases of concentrations with the axial distance are associated with the differences of the densities between issuing and surrounding gases, the decreases of velocities are proportional to the ratio of these densities. The differences of these behaviors for each gas are displayed by the contour maps of concentration and velocity. For lighter issuing gases, the velocities decay fast, but the concentrations remain at rather high values. On the other hand, for heavier gases, both oh the decays have considerably small values. And the results of experiments show that the turbulent exchange coefficients are proportional to a half power of those density ratios.