CORRELATION-COEFFICIENTS OF THE FLUCTUATING DENSITY IN TURBULENT PREMIXED FLAMES

Two-point density measurements by laser induced Rayleigh scattering ar e used in this study to fully characterise the scalar field in a Bunse n type turbulent premixed flame. The two points are separated within t he flame brush in the axial or radial directions. Correlation coeffici ents are obtained by comparing the evolution of one-point density fluc tuations in time or the two-point density fluctuations in both space a nd time. Time and length scales of the scalar field, and the mean conv ection velocity of the turbulent scalar structures are deduced from th ese correlation coefficients. Time scales are calculated from the auto -correlation coefficients, length scales are determined from the space correlation coefficients and the mean convection velocity of the scal ar structures in the axial direction is deduced from the space-time co rrelation coefficients. The relevance of these results for analysing a nd modelling the structure of turbulent premixed flames is discussed.