INVESTIGATION OF CHARACTERISTIC SCALES IN VARIABLE-DENSITY TURBULENT JETS USING A 2ND-ORDER MODEL

This paper is concerned with the investigation of characteristic turbu lent scales in circular and plane turbulent free jets with large densi ty variations. The numerical study has been performed with a second-or der turbulence model to confirm analytical relations about density and Reynolds number effects on dynamic and scalar turbulence scales deriv ed from requirements of pseudo-self-preservation. The present results explain and quantify trends previously reported from visualizations of variable density turbulent jets performed by Pitts (NBSIR Report No. 86-3340, U.S. Department of Commerce, 1986). It is clearly shown that the parameter relevant for the evolution of these scales is the moment um flux M(j). In addition, the influence of this quantity on small sca les is found to be larger than that on large scales.