Porous Flap Trailing Edges for the Reduction of Jet Installation Noise

Abstract

Integrating a modern jet engine underneath an aircraft wing can cause significant jet installation noise. This is especially true during take-off and landing, i.e. when the flaps are deployed. Part of the noise generation mechanisms for this so-called jet-flap interference noise is unsteady pressure fluctuations on the flap surface. An ideal noise reduction technology should preserve the steady flow properties while reducing pressure fluctuations. Porous materials maintain the flap contour geometry while reducing pressure fluctuations due to permeability between the flap pressure side and its suction side. The acoustic benefit is shown with help of experimental data from small-scale wind tunnel tests. Since other performance related parameters such as wing aerodynamics are slightly compromised, the use of porous flap trailing edges poses an interesting multidisciplinary optimization problem.