Beat of sound generated from NACA0012 airfoil on application of suction-blowing excitation.

This study investigates the generation of sound beats in the flow-induced noise from a NACA0012 airfoil subjected to periodic suction-blowing excitation (SBE) using direct numerical simulation (DNS) at a Reynolds number of 5000 and 5° angle of attack. The natural vortex shedding produces tonal noise at the Strouhal frequency (St), while SBE introduces an additional sound source at the forcing frequency (ff). Beats—rhythmic amplitude modulations in sound intensity—occur when ff is close to St and the sound intensities from both sources are comparable, with distinct propagation patterns differing from non-beat cases. The research identifies critical ranges of ff and excitation amplitude (Ae) that lead to beat formation in both the flow-normal and axial directions, emphasizing that appropriate selection of Ae is essential for beats to manifest. These findings enhance understanding of aeroacoustic phenomena relevant to noise control in applications involving laminar flow regimes such as small aerial vehicles.