Trailing edge noise from an isolated airfoil at a high Reynolds number

A multi-size mesh multi-time step strategy is used to perform three dimensional direct noise computations (DNC) around airfoils at high Reynolds numbers. This method allows to realize local grid refinements in conjonction with high order numerical methods commonly used in Computational AeroAcoustics (CAA). In order to analyse broadband trailing edge noise, the configuration consists in a truncated NACA0012 airfoil at high Reynolds 2.32 × 10 6 with an angle of attack of 2.5 ◦ and with triggered turbulent boundary layers both sides. This challenging case implies a wide variety of scales, and tackle the limit of the current computational capabilities. Two grids have been designed to test Large Eddy Simulations based on explicit filtering. In the present work, two of the five self-noise mechanisms due to specific boundary-layer phenomena identified and modeled by Brooks et al.[NASA Tech. Rep., 1989] are studied numerically. Namely, the noise radiation comes from the diffraction of the kinetic energy of evanescent waves advected in the turbulent boundary layers passing in the vicinity of the trailing edge in conjonction with the vortex shedding from the truncated trailing edge. First comparisons are made with an experimental database realized by the french aerospace agency ONERA. Particular attention is drawn to the characteristics of the wall pressure, in order to relate it with the acoustic field, obtained directly in the present approach.