Effects of roughness on broadband trailing-edge noise and propeller aerodynamic performance

The sustainability of the forthcoming air traffic growth is seriously compromised by high levels of noise emission. Rotating surfaces, such as rotors and propellers, are the most significant source of noise in many modern systems. Trailing-edge noise is the most important noise component for small scale rotors operating in low turbulence inflow. Trailing-edge noise is generated when a boundary layer encounters a sharp trailing edge. Since turbulent flow consists of eddies with varying sizes, the resulting noise is broadband. An additional source of noise is the tonal component, which occurs as a result of the blade passing frequency (BPF). Adequate modeling methods are important enablers in the noise footprint optimization process. Within the scope of this manuscript a three-dimensional model to estimate the broadband noise output of propeller trailing-edge noise was implemented. Following this, an experimental study to reduce noise output, including noise trip control with grit type tripping was conducted. The effects of this treatment on both noise output and performance were measured. Results show an improvement in noise output with negligible effects on propeller aerodynamic performance.