Velocity and Temperature Distributions for Cold Air Jets Issuing from Linear slot Vents into Relatively Warm Air

Abstract

Two-dimensional jets having various exit conditions were studied with a 15 cm field of view, laser-stimulated Mach Zehnder interferometer which provided isothermal contour maps, and with a pitot and thermoprobe traverse. At low discharge velocities (around 3 ms***), the onset of turbulence in the free air stream occurred further downstream of the nozzle than for higher efflux rates, and for vent widths of 2 mm and 4 mm the hypothetical source appeared downstream of the nozzle. However, at these low velocities, jet diffusion was more rapid after transition than for higher velocity cases. In general, the thermal boundary layer breadths were greater for narrower nozzle widths. To avoid excessive entrainment, the nozzle exit Reynolds number should exceed 1000.