Flow control mechanism of a compressor blade with a passive fluidic oscillator under varying attack angles

Passive fluidic oscillators integrated into compressor blades represent a passive flow control method. Unlike active flow control, their adaptability is particularly important for off-design operating conditions. However, the associated flow characteristics and control mechanism (especially under varying angle of attack conditions) remain unclear. To fill this research gap and clarify the influence of angle of attack on their control effect, this study investigates the flow control mechanism and adaptive characteristics of passive fluidic oscillators integrated into compressor blades under different angles of attack. Three-dimensional numerical simulations are conducted using structured grids and large eddy simulation, combined with dynamic mode decomposition (DMD) for unsteady flow analysis. Results show that their performance varies significantly with angle of attack: negative gain (increased total pressure loss) at small angles below 15°, positive gain at large angles above 15°, and optimal control at 18.9° (total pressure loss reduced by approximately 10%). DMD analysis reveals that the jet changes the dominant flow modes through frequency locking and synchronization with separation-induced vortices, with differential locking characteristics between the flow and the oscillator under varying angles of attack. This study clarifies the control characteristics and adaptive mechanism of passive fluidic oscillators under different angles of attack and provides guidance for the subsequent design and measures to further improve their adaptability.