Turbulent mixing of coaxial jets

Abstract

Experimental results on the turbulent mixing process between earbon dioxide and hydrogen central jets exhausting into a moving concentric stream of air are presented. The diffusion of mass and momentum only are considered, since both streams are at approximately equal temperature. The flow velocities are in the low to high subsonic range. Principal points of investigation are the condition of equal velocity between jets and the condition of equal mass flow per unit area between jets. Radial and axial distributions of concentration and velocity are presented. On the basis of the measurements, it is demonstrated that the product of local density and eddy kinematic viscosity coefficient can be assumed to be solely dependent upon the axial coordinate. Furthermore, it is concluded that no tendency toward segregation of the streams exists when either the velocities or the mass flows of the streams are equal. In agreement with previous results, it is found that mass appears to diffuse more readily than momentum. Finally, a formulation of the eddy viscosity and eddy diffusivity coefficients that adequately describe the results obtained is derived.