Flow control and wake vortex dynamics induced by trailing edge serrations in cascade blade

Abstract

Trailing-edge (TE) serrations serve as an effective flow control strategy with the superior wake-flow adaptability. While existing studies are mainly focused on overall aerodynamic benefits of blade cascade, the underlying wake/vortex control mechanisms, particularly the effects of serration spanwise positions, remain to be further understood. Based on aerodynamic performance tests in a cascade wind tunnel, the accuracy of computational fluid dynamics numerical model is validated. Then considering the different incidences and Mach numbers, flow wake and vortex dynamics are analyzed in tip/middle/root spanwise positions. The results show that the serrated TE significantly reduces aerodynamic loss and improves flow characteristics of the blade cascade. Compared to the baseline, the average ω of serrated cascade decreases by 7.05% at 0.4Ma and 0° incidence. For the role of serration, the tip region exhibits the largest reduction of 16.2% in total pressure loss, the middle region significantly promotes momentum transport and turbulent mixing, and the root region achieves pressure fluctuation attenuation. This is mainly attributed to the serration-induced jet flow and wake-vortex breakdown. In addition, different incidences and Mach numbers have a sensitive effect on aerodynamic performance of serrated cascades. Relative to the baseline cascade, the moderate positive incidence can contribute to reducing unsteady pressure fluctuations and flow stability, and the middle region of serration at 0.7Ma exhibits a maximum local reduction of 35.9% in total pressure loss. These findings provide a theoretical basis and engineering guidance for the high-performance biomimetic blade design.