THE EFFECT OF ASPECT RATIO ON THE NEAR-FIELD TURBULENT STRUCTURE OF ELLIPTIC JETS

Abstract

The near-field turbulent structures of elliptic jets issuing from sharp-edged elliptic slot nozzles were experimentally investigated using a 3D LDV system. To examine the effect of the slot aspect ratio on the flow characteristics of the elliptic turbulent jet, we have used elliptic slot nozzles with aspect ratio AR = a/b = 1, 2, 4, 8 having the same equivalent diameter (D(e) = 2 (ab)1/2) of 60 mm; the Reynolds number, based on D(e), is 4 x 10(4). An elliptic jet issuing from a sharp-edged nozzle had higher mean streamwise velocity decay rates than a contoured nozzle jet due to the effect of the extremely slender elliptic vortical structure. Also, there was a remarkable difference in the jet spreading rates along the major and minor axes. The effects of aspect ratio on the turbulence characteristics of the elliptic jet were apparent, and in particular the elliptic jet of AR = 2 showed vigorous turbulence characteristics in the near flow fields.