Effects of turbulence length-scale distribution on scalar mixing in homogeneous turbulent flow

Abstract

The linear eddy mixing model is used to study effects of the turbulence length-scale distribution on the transient evolution of a passive scalar in a statistically steady homogeneous turbulent flow. Model simulations are carried out using both wide-band length-scale distributions reflecting high-Reynolds-number scaling, and narrow-band (in effect, low-Reynolds-number) distributions. The two cases are found to exhibit qualitative differences in mixing behavior. These differences are interpreted mechanistically. The narrow-band case yields the best agreement with published direct numerical simulation results, suggesting that those results are, in effect, low-Reynolds-number results not readily extrapolated to high-Reynolds-number mixing.

Linear eddy modeling of reactant conversion and selectivity in turbulent flows

“…In Figure 3 single length-scale version of the model are presented. Cremer et al (1994) show that with l*/L=5/12, this variant of the model is more representative of the mixing processes studied by DNS. In this case, as shown in Figure 3, the asymptotic value of the unmixedness ratio is indeed close to 2/?r and is in better agreement with predictions via AMC and DNS.…”

“…In this case, as shown in Figure 3, the asymptotic value of the unmixedness ratio is indeed close to 2/?r and is in better agreement with predictions via AMC and DNS. This feature of LEM has been discussed in detail by McMurtry et al (1993a) and Cremer et al (1994). The conclusion is that a "narrow-banded" mixing process, as characterized by a larger value of p , or a single length scale version of the model is more characteristic of the moderate& mixing of DNS.…”

“…In particular from Eqs. 3-4, it is noted that an increase of the magnitude of p Cremer et al (1994) show that an extreme representation of scalar mixing a single length scale I * , that is:…”

“…Since its original development, LEM has been used extensively to study various aspects of turbulent mixing and combustion processes. Applications to date include analyses of turbulent reacting shear flows (Kerstein, 1989), turbulent diffusion flames (Kerstein, 1990), turbulent premixed flames (Menon and Kerstein, 1992), mixing in homogeneous turbulent flows (Kerstein, 1991a,b;McMurtry et al, 1993a;Cremer et al, 1994;Frankel, 1993) among others; an up-to-date review is available (McMurtry et al, 1993b). These contributions have been very useful in capturing the physics and in motivating further research on several important features of turbulent reacting flows.…”

An Engineering Model for Designing Compact Toxic Waste Incinerators

“…Note that this approach is not unique to this study. Earlier mixing studies by Cremer, McMurtry and Kerstein (1994) …”