Numerical study of aeroacoustics of an NACA0018 airfoil with a cavity at various angles of attack

This paper reports the progress of a two dimensional numerical study of the aeroacoustics of NACA 0018 airfoil with a cavity at −4° and 4° angles of attack, with chord based Reynolds and free-stream Mach numbers at 2 × 10⁴ and 0.2. In addition to the vortex shedding at the airfoil trailing edge, the shear layer at the cavity oscillates in different modes at these two angles of attack. Wavelet analyses indicate that little switching between different types of flow dynamics. The airfoil at these angles of attack produces more noise than the airfoil does at zero angle of attack. Although the presence of a cavity introduces additional acoustic generation due to cavity oscillation modes, the vortex shedding at the airfoil trailing edge remains the major acoustic generating process. Since these flow processes operates at different distant frequencies, the acoustic contribution of these processes can be easily discerned in the spectral analyses.