TURBULENT PRANDTL NUMBER IN A CIRCULAR JET

Measurements of the Reynolds shear stress and heat flux distributions at a number of streamwise stations in a heated circular jet into still air indicate that the flow is approximately self-preserving at x d = 15. Measurements made with a 120° X-probe are in closer agreement with calculations obtained by integrating the mean momentum and mean enthalpy equations than measurements made with a 90° X-probe. The turbulent Prandtl number increases near the edge of the jet but, in a region between the axis and the jet half-radius, it is approximately constant (0.81 ± 0.05). This numerical value is in reasonable agreement with that selected by So and Hwang (ZAMP 37, 624-631 (1986)) for similarity solutions of non-isothermal round jets. It is suggested that the early attainment of self-preservation in the present flow may be due to the laminar conditions at the jet exit. © 1990.