Direct self-noise simulation of the installed Controlled Diffusion airfoil

Abstract

Broadband noise produced by the trailing-edge of a controlled di usion (CD) airfoil is directly simulated using a Lattice-Boltzmann method (PowerFlow) that resolves both the aerodynamic and acoustic eld around the airfoil. The proper DNS resolution is rst achieved in the vicinity of the airfoil on a quasi-2D slice of the mock-up. It is then extended to a 3D slice with a span of 12 % chord length. Two numerical setups of the anechoic openjet facility where both aerodynamic and acoustic data have been collected are investigated to capture the installation e ects: in a rst numerical setup (called free), the CD airfoil is set in an uniform ow, while in the second setup (lips) the real jet nozzle geometry is considered. While in the freeeld con guration the boundary layer rapidly detaches on the suction side, in the lips the jet shear layers modify the pressure load on the airfoil and the boundary layer keeps attached in the con guration with nozzle. In both setups a laminar recirculation bubble is captured on the suction side near the leading edge which triggered the development of the boundary layers along the suction side. The wall-pressure and noise spectra for the free con guration are spread over a large frequency band and agree with similar measurements at higher angle of attack for which the ow is detached. The spectra for the lips con guration better agree with the experimental data and has been selected for the 3D simulation. The vortex stretching along the span-wise direction that was missing in the previous investigated set-ups, allows to nely capture the turbulence length scales and accurately reproduce the experimental measurements. Both the boundary layer pro le and the wall pressure spectra near the trailing edge are nicely and accurately captured. The predicted fareld sound pressure levels also provide satisfactory agreement with noise measurements in the anechoic wind tunnel.