Numerical studies of chemical selectivity and heat transfer in decaying homogenous turbulence

Abstract

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Direct numerical simulation of chemical selectivity in homogenous turbulence

“…According to Levenspiel (1972), if there is any nonhomogeneity in A and R, the formation of S is favored, since the reaction zones (zones between regions of high A concentration and high B concentration) contain higher concentrations of R than the surrounding regions, and there is thus a steep concentration gradient and R mixes and reacts with B to form S. But if A and R are spatially homogenous or are present together, they can compete with each other for the B present and produce more R or S. If they are not spatially homogenous, then R reacts with B to form S. These situations are comparable to the case where B is added slowly to a mixture of A and to the case where A is Table 2 added slowly to a mixture of B, respectively, as described by Levenspiel (1972). Thus, segregation of reactants favors formation of S , whereas homogenization favors formation of R. A more detailed discussion on the subject is available in Chakrabarti (1991). Effect of Turbulence Reynolds Number.…”

“…scales are given in Chakrabarti (1991). In the present study, the simulations used an initial Gaussian energy spectrum ( X ) , unless otherwise mentioned.…”

“…In direct numerical simulations (DNS), the nonlinear dynamical equations are solved with no turbulence modeling and with all time and length scales well-resolved. Direct numerical simulations of three-dimensional chemically reacting homogenous turbulent flow for unmixed reactants in a single step, finite rate reaction have been made by Givi and McMurtry (1988), Leonard and Hill (1988, 1989, 1991 and Me11 et al (1993). Some preliminary investigations on the effect of various physical and chemical parameters for the seriesparallel reaction case have been made by Chakrabarti and Hill (1990) for decaying homogenous turbulence and by Gao and O'Brien (1991) for a forced turbulent flow.…”

“…The theoretical and measured (in simulations) values of the integral length scale, Taylor microscale and Kolmogorov microscale for the different spectra are also shown in Table 1. The details of the derivations of the theoretical forms of the length *Derivations for constants a and b and the different length scales are given in Chakrabarti (1991). The peak wave number, k, is 2.5 and the cut-off is…”

Linear eddy modeling of reactant conversion and selectivity in turbulent flows

“…This work uses the LEM to investigate the mechanisms of turbulent reacting flows which are of importance to chemical engineering. For this purpose, the prediction of the reactant conversion in nonpremixed homogeneous turbulent reacting flows is studied considering the same reaction schemes as those used in previous DNS (a single-step reaction mechanism and a series/parallel scheme) (Givi and McMurtry, 1988;McMurtry and Givi, 1989;Gao and O'Brien, 1991;Chakrabarti and Hill, 1990;Chakrabarti, 1991). Model simulations are conducted over a wide range of the flow parameters consisting of the Reynolds number, the Schmidt number, and the Damkohler number(s) to study the effects of these parameters on the statistics of the reacting scalars.…”