Aerodynamic and Aeroacoustic Characteristics of the NACA 0008 Airfoil

This paper discusses the flow dynamics and the leading- and trailing-edge noise generated by a NACA 0008 airfoil to better understand the near- and far-field noise characteristics of thin airfoils. Experiments were performed in the Aeroacoustic Wind Tunnel of the University of Twente for a chord-based Reynolds number ranging from 3.2×10⁵ to 1×10⁶. The measurements consisted of static pressure along the chord, boundary layer at the trailing edge, wall-pressure fluctuations along the chord, and far-field radiated noise. The pressure distribution along the airfoil chord, the lift coefficient, and the boundary layer characteristics at the airfoil trailing edge for different angles of attack are discussed and compared with XFOIL simulations, showing a good agreement. In case of no inflow turbulence, trailing-edge noise is dominant. The wall-pressure fluctuations at the trailing edge and the far-field noise are slightly affected by the angle of attack. At stall, the energy content of the wall-pressure fluctuations in the low-frequency range and the spanwise correlation length increase considerably. In case of inflow turbulence generated by a rod, the wall-pressure fluctuations along the airfoil chord are strongly influenced by the inflow turbulence. The highest energy content of the wall-pressure fluctuations is at chordwise positions close to the leading edge. Leading-edge noise is the dominant noise source for low- and mid-frequencies. However, trailing-edge noise level is comparable with the leading-edge noise for high frequencies.