Investigation of characteristic scales in variable density turbulent jets using a second-order model

Abstract : This paper is concerned with the investigation of characteristic turbulent scales in circular and plane turbulent free jets with large density variations. The numerical study has been performed with a second-order turbulence model to confirm analytical relations about density and Reynolds number effects on dynamic and scalar turbulence scales derived 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 momentum flux Mj . In addition, the influence of this quantity on small scales is found to be larger than that on large scales.