INFLUENCE OF LEADING EDGE TUBERCLES IN AN ANNULAR COMPRESSOR CASCADE WITH DIFFERENT HUB-TIP RATIOS AND ASPECT RATIOS

Humpback whale flippers' scalloped tubercles on the leading edge are thought to enhance the whale's underwater maneuverability. Inspired by the flippers, leading edge tubercles are applied in a low speed annular compressor cascade as a type of passive flow control techniques in this paper. A numerical study is performed to investigate the influence of tubercles on the aerodynamic losses and corner separation in the low speed cascades. Different low speed cascades based on a CDA airfoil profile are built with several hub-tip ratios and aspect ratios. Steady RANS simulations are carried out for these cascades with and without leading edge tubercles. The aerodynamic performance and corner separation features are subsequently investigated in these cascades. The influence of tubercles under the variation of hub-tip ratio and aspect ratio is understood and concluded from the comparison of the performance attained by different cascades. Flow visualizations at a post-stall incidence angle show that the interaction between the tubercle-induced streamwise vortices and corner separation vortices plays a crucial role in attenuating the corner separation and reducing losses. By combining the performance analysis and flow visualizations, this paper discusses the mechanism of leading edge tubercles in a low speed annular compressor cascade with different hub-tip ratios and aspect ratios.