Superiority of Tabs with Corrugations on Jet Mixing

Abstract

The jet mixing promoting effectiveness of two identical rectangular tabs of blockage 2.5% (each), placed diametrically opposite at the exit of a Mach 1.65 axi-symmetric nozzle, is experimentally investigated. The efficacy of the tab with and without corrugations is studied at varied levels of expansions present at the nozzle exit. To quantify the tab performance the total pressure distribution along and across the jets were measured at varied Nozzle Pressure Ratios (NPRs). The shocks and expansion fans prevailing in the uncontrolled and controlled jets were visualized by shadowgraph technique. It is seen that when the plain tabs are introduced at the nozzle exit, only a 37.5% reduction in core length is obtained at over-expanded conditions corresponding to NPR 4 whereas, providing corrugations along the tab edges has affected their performance drastically. The efficacy of corrugated tabs is found to be superior at under-expanded condition with a maximum core length reduction of 90.1% at NPR 6. The pressure profile plots also confirm that the corrugated tab is more efficient in promoting the mixing, without introducing asymmetry to the jet field. In addition to reducing the core length, the corrugated tab causes the waves in the core to become weaker and the shock cells to become shorter, compared to the uncontrolled jet.

Keywords: Supersonic jet core, shock-cell length, jet mixing, noise attenuation, shadowgraphic flow visualization

Cite this Article

Mrinal Kaushik. Superiority of Tabs with Corrugations on Jet Mixing. Journal of Aerospace Engineering and Technology (JoAET). 2015; 5(3):        15–26p.