Study of the Noise Reduction Mechanism of Bionic Circular Arch Structures on the Blades of a High-Volumetric-Airflow Axial Flow Fan.

While bionic sawtooth and wave structures effectively reduce aerodynamic noise on fixed airfoils, their efficacy on rotating fans is often limited. Inspired by the protrusion structures of dragonfly wings and the gentle circular arches of manta rays, this study proposes a novel bionic circular arch structure to suppress aeroacoustic noise in axial flow fans. Numerical simulations were validated against experimental data from a standard fan, showing a sound pressure level (SPL) deviation within 3 dB at the first blade passing frequency (BPF), confirming calculation accuracy. The results indicate that the bionic design reduces the total SPL by approximately 2.5 dB. Notably, in the human-sensitive frequency range of 1000-3000 Hz, noise reduction reaches up to 6.6 dB at the upstream monitoring point. Analysis of Root Mean Square (RMS) fluctuating pressure and Fourier transforms reveals that the bionic structure significantly mitigates noise source intensity at the blade tip. This design effectively reduces pressure disturbances at the first BPF and shrinks the high-intensity disturbance region of the boundary layer compared to the prototype.