Measurements of Prandtl Number of an Elliptic Jet

Abstract

The turbulent Prandtl number, Pr_t, distributions of a heated contoured contraction nozzle elliptic air jet with a 2:1 aspect ratio issuing into stagnant, unconfined surroundings were presented. The measurements were carried out with X-wire and three-wire (a cold wire in front of an X-wire) probes. The normalized RMS velocities in both lateral and span-wise directions were consistently smaller than those in the streamwise direction, indicating the anisotropy of the turbulence in the flow. The Pr_t evaluated based on the self-preserved data of Reynolds shear stress, $\overline{\text{uv}}$, and heat flux, $\overline{{{\text{v}}\uptheta}}$, at ${\text{x}} = 30{\text{D}}_{\text{e}}$ decrease sharply from the center and only remained at a constant value of about 0.8 within the range of $0.4 \le {\text{y}}/{\text{L}}_{\text{y}} \le 1.8$ along the major axis while a gradual increase is observed in the minor axis. A constant Pr_t in both axes should not be granted in the computational modeling and analysis of a heated elliptic jet.