Effect of Air Tab Orientation on the Mixing and Spreading Characteristics of a Subsonic Jet

Abstract

The aim of this experimental study is to investigate the influence of air tab orientation on the mixing and spreading behavior of a Mach 0.8 primary jet ejected from an axisymmetric nozzle. Two air tabs have been considered in two configurations, namely, 90° and 45°, with respect to the primary jet centerline. The air tab Mach numbers, ranging from 1.1 to 1.4 in an interval of 0.1, have been considered. The jet decay along the primary jet centerline (X), along the lateral (Y), and vertical (Z) directions have been acquired. The jet half-width also has been calculated to assess the mixing/spreading enhancement induced by air tabs along the lateral and vertical directions. The percentage reduction in potential core achieved by 90° air tabs is higher than that of the 45° air tabs at all the Mach numbers studied. The 90° air tabs contract the primary jet along the vertical direction and expand it along the lateral direction. This implies a better jet mixing enhancement in the vertical direction and improves spreading along the lateral direction. On the other hand, the 45° air tabs result in rapid jet decay along both directions, in the far-field locations. The present study reveals that the 90° air tabs are best suited for applications that require better jet mixing, while the 45° air tabs are suitable for moderate jet mixing with the minimum total pressure loss.