DATA ANALYSIS OF TWO NON-ISOTHERMAL TURBULENT JETS

Abstract

A three-component Laser Doppler Anemometer (LDA) instrument, an array of stationary thermocouples and a moving thermocouple were used to capture the three-dimensional flow and temperature fields for the system of two opposing axisymmetric turbulent jets. It was found that buoyancy-induced curvature of the hot jet resulted in cross shearing with the opposing jet. The following report will investigate the adequacy of the current experimental measurements for the identification of coherent structures and the characterization of their effects on the mean flow. Identification tools include the power spectra and conditional average velocity measurements based on the Window Average Gradient (WAG). It was determined that the low sampling and large spatial positions of the thermocouple measurements were not for the retrieval of quantitative turbulence data. For the velocity measurements, the LDA data were found to be adequate in regions of low turbulence intensities but degraded as the measurements approached the region where the two jet shear layers interacted. The detection of periodic structures from the power spectrum was inconclusive due to noise. The WAG algorithm was affected by the irregular sampling and required modification. For the events detected, an intermittency factor of 16.4% at the interaction region of two shear layers was observed. In addition, these results suggest that these events contribute 30% of the mean momentum transfer across the jet. Furthermore, the contribution of these events to the lateral component of the turbulent kinetic energy was nearly eight times larger than the contributions to the axial or transverse direction.