Interaction Region of a Two-Dimensional Turbulent Plane Jet in Still Air

Abstract

Mean velocity and temperature profiles in the interaction region of a slightly heated turbulent plane jet with initially laminar boundary layers do not deviate perceptibly from the far field self-preserving profiles when the centreline mean velocity/temperature and mean velocity/temperature half-widths are used as the appropriate normalising scales. On the jet centreline, the maximum value of the ratio of rms to mean temperature is larger by a factor of almost two than the corresponding ratio for any of the three velocity fluctuations. The probability density function of temperature on the centreline and at a distance of twelve slit widths from the nozzle reveals the presence of room temperature fluid and also of fluid which is at the jet exit temperature. Spectral density functions of temperature exhibit a peak up to a distance of about twelve nozzle widths. Space-time correlations of velocity fluctuations indicate that the vortical structures, symmetrical with respect to the centreline, which are observed at the beginning of the interaction are replaced by structures, asymmetrical with respect to the centreline, towards the end of the interaction region.