Leveraging surface aeroacoustic-structural interaction for airfoil tonal noise reduction

In this paper, a passive method of airfoil tonal noise control is investigated by using an elastic panel flush mounted on the suction surface of a NACA 0012 airfoil at an angle of attack of 5⁰ and flow velocity of Mach number 0.4. Direct Aeroacoustics Simulation along with Linear Stability Analysis is used to study the interaction between airflow and elastic panel mounted on suction surface of airfoil. Panel parameters are carefully selected to ensure that the natural frequency of panel in the presence of flow field is similar to that of flow frequency. A parametric study is carried out based on different panel parameters including material density, panel thickness and internal tension to analyze the sensitivity of parameters on panel response to instability wave over the airfoil, subsequently modifying panel vibration behavior and reducing the tonal noise. Six different cases are analyzed and their performance is evaluated in terms of tonal noise reduction. Numerical results indicate a significant improvement in noise reduction is achieved for all cases as compared to previous study. Contribution of panel density and thickness in noise reduction are found to be dominant based on comparative study.