Tabs protruding into jet flows are known to significantly enhance the mixing and increase the jet spread rate. The primary mechanism for effective noise reduction by tabs has been identified in earlier studies as streamwise vortices generated from the tab vertices. Based on the encouraging results from triangular and rectangular tabs this study investigates inverted triangular tabs which have the benefit of rectangular tabs but the blockage of triangular tabs. In the proposed work, the effect of inverted triangular tabs on the aero-acoustics is compared with that of triangular tabs. While tabs in general reduced the acoustic levels significantly as compared to the baseline nozzle (without tabs), the inverted triangular tabs were found to be more effective than the triangular tabs. The penalty in increase of high frequency noise associated with use of tabs was at par or lower than the triangular tab configuration. Although both type of tabs are found to be effective for underexpanded flows, the effect reduces at M_j≥1.6. OASPL directivity patterns indicate that inverted triangular tabs perform as good as or better than triangular tabs in reducing noise levels by ～7 dB as compared to ～5dB. Under a certain underexpanded condition, the inverted tabs are found to reduce the broadband shock associated noise by 12 dB as compared to 7dB in the case triangular tabs. Overall it is evident that inverted triangular tabs offer higher benefits compared to triangular tabs in terms of lower noise levels at all jet operational conditions.
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