A. J. Lightman
Published: 1983
Total Pages: 139
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A two-dimensional laser Doppler anemometer was designed to take measurements in a ducted coaxial flow system having a centerbody separating the jets. The measurements, made in isothermal flow, can be categorized as: central jet only (C02); annular jet only (air); and, combined central and annular jet flow. Radial profiles of the axial and radial/azimuthal velocity were obtained. The central jet only condition approximates a free jet since the central jet diameter is much smaller than the centerbody or duct diameter (1:29.3: 53.2). Measurements of the jet development (diameter, turbulence intensity, etc.) were compared with previous free jet studies. In a study of the isotropy of the turbulent fluctuations it was determined that fully developed turbulent flow begins further downstream than anticipated. Velocity profiles were combined with gas sampling measurements to ascertain jet entrainment. Results show a linear growth of the entrained mass starting at the entrance plane. Downstream (20 diameters) the rate of growth increases to match past studies in that region. The annular jet flow creates a recirculation vortex in the wake of the centerbody. The flowfield was mapped and the streamlines describing the flow were obtained throughout the recirculating flow and further downstream. The location and strength of the vortex center was determined. Velocity scanes were combined to obtain profiles of the average radial and azimuthal components that were directly measured. The interaction of the recirculating annular air jet and the central get was examined. Profiels of the velocity field were obtained for several central jet flow conditions. A normalization plot of the location of the central jet stagnation location agreed well with earlier measurements using a one-dimensional laser doppler anemometer and a different central jet nozzle.