Passive control of aerodynamic noise from tandem airfoils using a micro-perforated leading-edge array on the downstream airfoil

Abstract

To address turbulence-interaction noise induced by strong wake–leading-edge interactions in tandem airfoils of turbomachinery, this study considers National Advisory Committee for Aeronautics 6412 tandem airfoils and designs three micro-perforated array configurations with different chordwise coverages at the leading edge of the downstream airfoil. Acoustic wind tunnel noise measurements, transient particle image velocimetry flow-field measurements, and proper orthogonal decomposition analysis are combined to systematically investigate the acoustic characteristics and noise-reduction mechanism. The results show that pronounced discrete tonal noise peaks are generated when the downstream airfoil is located within the core region of the upstream wake. The micro-perforated array with a chordwise coverage of 12.4% achieves a maximum noise reduction of 15 dB in the dominant noise-frequency band of 400–2000 Hz, completely suppresses the discrete tonal noise peaks, and reduces the overall sound pressure level by approximately 5 dB across the measured polar range of 75°–120°, and no notable change in far-field noise directivity is observed within this angular coverage. The primary noise-reduction mechanism is that the leading-edge permeability effect weakens near-wall separation vortices and turbulent fluctuations, disrupts the large-scale periodic vortex street formed by wake-wall coupling near the downstream leading edge, and promotes the cascade and dissipation of unsteady energy into higher-order small-scale modes. These findings can be applied to reduce noise in rotating machinery, such as guide blade rows, fan blade rows, and turbine blade rows.