Corrugated triangular tabs for supersonic jet control

This article presents the effectiveness of a tab shedding small-scale vortices of continuously varying size, in enhancing the mixing of axisymmetric Mach 2 jet at different levels of expansion. Corrugations in the form of semicircle, triangle, and square geometries located on the slanting edges of two identical isosceles triangular tabs, placed at diametrically opposite locations of the circular nozzle exit have been studied. The corrugated tabs are found to be the better mixing promoter than uncorrugated tabs. Among the corrugation geometries, the semicircular corrugation with two sharp corners is found to be the best mixing promoter in the presence of marginally overexpanded and almost zero pressure gradients, for the Mach 2 jet. However, for a highly overexpanded state, the performance of semicircular and square corrugated tabs is comparable. A reduction in core length as high as 90% was achieved with semicircular corrugation tabs, compared to uncontrolled jet in the presence of marginally adverse pressure gradient, corresponding to nozzle pressure ratio 7.