Mixture fraction field in a turbulent nonreacting propane jet

Time- and space-resolved mixture fraction measurements have been made throughout a turbulent nonreacting propane jet issuing into coe owing air using laser Rayleigh scattering. The objective of the measurements has been to obtain a better understanding of the e ow structure and mixing process in turbulent variable-density jets where turbulent mixing has been decoupled from the effects of chemical heat release found in highly exothermic reacting jets. The measurements yield probability density distributions of the mixture fraction, from which the means, higher moments, and intermittency are calculated. Time histories of the Rayleigh signal are analyzed to obtain the power spectra and autocorrelations. Comparisons are made with results for other constant- and variable-density turbulent jets, and the observed differences are discussed. I. Introduction T HE development of numerical models for turbulent reacting e owsisbasedlargelyonsubmodelsdevelopedfornonreacting, constant-density e ows. Verie cation of these submodels is often dife cult due to the complex interaction between turbulent mixing and combustion heat release. Previous evidence indicates that the use of submodels based on isothermal or nonreacting turbulent e ows may not be valid in reacting e ows. 1i 3 The turbulent, variable-density, nonreacting jet provides a simplie ed e ow situation in which the complexity of variable density remains without the complex coupling between turbulent mixing and chemical heat release. Thus the effects of variable density on turbulence can be isolated from combustion chemistry. Nonreacting, variable-density e ows form a logical bridge between nonreacting constant-density and reacting turbulent e ows in which the development of a database is necessary to the development of numerical models for turbulent reacting e ows.