Measurement of scalar-velocity correlations in a turbulent diffusion flame

Abstract

Simultaneous measurements of scattered light intensity and axial velocity have been made in a turbulent hydrogen diffusion flame in a co-flowing stream with accelerating and decelerating pressure gradients. The light-scatter signal obtained from the seeded nozzle fluid is used as a measure of hydrogen element concentration, and is processed to derive records of density and mixture fraction which are correlated in digitized form with the simultaneously recorded streamwise velocity component. Results reported here include the mean and r.m.s. fluctuation of the streamwise velocity component and the density and correlations of the streamwise velocity component with the mixture fraction and the density as well as other correlations and Favre or density weighted averages. It is shown that the density velocity correlation is only large enough to make a few percent difference between the Favre and conventional mean velocities but that such correlations are important in the determination of the excess momentum flux. Correlations between velocity and mixture fraction are comparable with those found in isothermal flow but change sign where the excess velocity changes sign. The correlation between density and velocity shows similar behaviour and is shown to have a significant effect on the turbulent kinetic energy balance.