Some Budgets of Turbulent Stresses in Round Jets and Diffusion Flames

Abstract

Measurements are presented of budgets of shear stress, normal stresses and turbulent kinetic energy in a round air jet and in two H₂ diffusion flames, all in a co-flowing air stream. The results are based on simultaneous two-component LDA and Mie-scattering measurements, and are presented in Favre averaged form. The flames show basically similar features to the cold flow, but overall magnitudes of the normalized terms are lower, and the advection contribution to turbulent kinetic energy is much reduced. The turbulence dissipation rate ε is obtained from the budgets of turbulent kinetic energy by difference, and is used later to obtain values of the velocity pressure-gradient correlations u ∂p/∂x and ν ∂p/∂r, again by difference. The results are consistent with other published estimates of these terms; whilst they seem small in the turbulent kinetic energy balance, they dominate in the budgets for the stresses, and are largely balanced by production. A comparison with a well-publicized numerical model for the pressure terms shows good agreement when model constants found in the literature are used.