Tractor Propeller-Pylon Interaction, Part II: Mitigation of Unsteady Pylon Loading by Application of Leading-Edge Porosity
55th AIAA Aerospace Sciences Meeting
Structure-borne noise can be a relevant source of cabin noise in advanced aircraft configurations with pylon-mounted tractor propellers. The periodic impingement of the propeller slipstream on the pylon causes unsteady loading that can be mitigated by applying passive porosity at the leading edge of the pylon. Pressure reconstruction from particle-image velocimetry was used to extract the unsteady pressure field around the pylon and the associated aerodynamic loads. Experimental results showed
... tal results showed that porosity locally modifies the pylon near-wall pressure distribution because of the crossflow through the porous surface. Application of a porous leading edge reduced the intensity of the unsteady pressure fluctuations in the tip-vortex impingement region by approximately 5% and 30% on the suction and pressure sides of the pylon, respectively. Consequently, the unsteady pylon loading induced by the propeller tip vortices was reduced by 25%, thus resulting in a less intense source of vibrations. On the other hand, pylon drag was locally increased. Based on the experimental data, projections of the drag penalty were made for a generic pylon design. The resulting pylon drag penalty equaled 15% up to 35% for angles of attack of 0 • up to 9 • . This drag penalty was attributed to the early onset of transition caused by the increased surface roughness of the porous insert, and viscous dissipation of the crossflow through the cavity of the porous insert. * M. Sc. Student, Fac. of Aerospace Eng., Bia.DellaCorte@studenti.unina.it.