Abstract
An experimental investigation has been carried out to examine the effectiveness of air-tabs in controlling the subsonic and correctly expanded sonic jets. The primary/main-jet was controlled by the air-tab (control-jet) of different diameter and exit Mach numbers. The Mach number decay along the jet centerline and the Mach number profiles along and normal to the air-tabs were determined from the measured Pitot pressures. Increase in mass ow rate of the control-jet or air-tab results in reduced potential core length, thereby better mixing. The distortion introduced by the air-tab increases with increase in Mach number, mass ow rate and decrease in diameter of the air-tab. A 20% reduction in main-jet local Mach number can be brought about by a control-jet mass ow of 4.04% of the main-jet mass ow from the smaller air-tab (d/D = 1/8.33), whereas the same reduction with larger control nozzles (d/D = 1/6.25 and 1/5.0) requires a control-jet mass ow of 7.0% and 12.6%, respectively. Moreover, the air-tabs with smaller diameter, exhibit higher distortion of the jet and resultant increase in jet mixing. Therefore, air-tab of smaller diameter was found to perform better than the higher air-tab diameters. A combination of, Mach number ratio, mass ow ratio and diameter ratio, was found to have a direct in uence in the jet spread and mixing.
Published Version
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