Aerodynamics of Wedge-Shaped Deflectors for Jet Noise Reduction,” AIAA Paper 2006-3655

A wedge-shaped deflector placed in the fan exhaust of a turbofan engine can reduce jet noise in a range of azimuthal directions opposite the wedge. The aerodynamics of the fan flow deflector (FFD) wedge are investigated with pressure surveys and flow visualization. The flow field is found to differ substantially from that of a classical wedge-shaped cylinder. There is a significant force developed on the side of the FFD wedge, whereas the classical wedge develops nearly zero side force. The base pressure coefficient of the FFD wedge is substantially less negative than that of the classical wedge. Consequently, the FFD wedge develops about 75 % less drag than one would have expected from 2D wedge data. Nomenclature c = wedge chord length CD = sectional drag coefficient CL = sectional lift (sideforce) coefficient CP = pressure coefficient h = wedge height M = Mach numbers NPR = nozzle pressure ratio=p0/pa p = pressure u,v,w = velocity components U = free stream velocity V = velocity magnitude = (u2+v2+w2)1/2 x,y,z = Cartesian coordinates α = wedge half angle γ = specific heat ratio ρ = densit