On turbulent diffusion in coaxial jets of dissimilar gases with pressure gradient

Focusing the attention upon the field with the axial pressure gradient, the turbulent diffusion in the coaxial jets of dissimilar gases was investigated theoretically. Dealing with the mean values of the turbulent flow, the turbulent diffusion coefficient was modeled by means of employing the solutions for the linearized species equation as obtained by Libby and Kleinstein. The turbulent wake equations involving this diffusion model were solved numerically. Comparing these solutions with the existing experimental results, the following conclusions are drawn: (1) for the jet mixing without the pressure gradient, the present diffusion model provides excellent predictions of axial and radial profiles both for concentration and velocity; (2) for the case with large axial pressure gradient, the axial profile of concentration and temperature could be predicted satisfactorily, but the velocity profile could not; and (3) though Sc sub t, Pr sub t and Le sub t were proved to be constant throughout the mixing field without pressure gradient, Sc sub t was found not to be constant for the case with pressure gradient.