Direct noise computation of the turbulent flow around a zero-incidence airfoil

A large eddy simulation of the flow around a NACA 0012 airfoil at zero incidence is performed at a chord-based Reynolds number of 500,000 and aMach number of 0.22. The aim is to show that high-order numerical schemes can successfully be used to perform direct acoustic computations of compressible transitional flow on curvilinear grids. At a Reynolds number of 500,000, the boundary layers around the airfoil transition from an initially laminar state to a turbulent state before reaching the trailing edge. Results obtained in the large eddy simulation show a well-placed transition zone and turbulence levels in the boundary layers that are in agreement with experimental data. Furthermore, the radiated acoustic field is determined directly by the large eddy simulation, without the use of an acoustic analogy. Third-octave acoustic spectra are compared favorably with experimental data. Nomenclature Cf = skin-friction coefficient, f=0:5U21 Cp = mean-pressure coefficient, p p1=0:5U21 c = chord length of the airfoil c0 = sound speed in the medium at rest H = boundary-layer shape factor, = M = Mach number, U1=c0 Rec = Reynolds number based on the airfoil chord, U1c= Re = Reynolds number based on the momentum thickness tc = convection time across the airfoil, c=U1 U1 = upstream flow velocity u = wall-friction velocity