Influence of Roughness Trips on Near- and Far-Field Trailing-Edge Noise

Roughness trips are widely applied in wind-tunnel testing to hasten the laminar–turbulent boundary-layer transition. It is well known that they influence transition and its development. However, their on aeroacoustic quantities (in particular, airfoil trailing-edge noise) not yet fully understood. This paper discusses relationship between trip height development radiated noise. Wind-tunnel experiments were performed with zigzag strips grit elements placed surface of a NACA 0012 airfoil. The roughness heights ranged from 17 214% undisturbed thickness at location. chord-based Reynolds number varied . shows within 50 105% have little near field increase spectra velocity pressure fluctuations low-frequency range up 2.5 3 dB, respectively, resulting an noise 4 dB similar frequency range. In summary, this importance carefully defining used trigger aerodynamic measurements.