Aeroacoustic Simulations of a Simplified High-Lift Device Accounting for Some Installation Effects

Abstract

The aeroacoustic noise of a simplified wing-flap configuration placed in an open-jet anechoic wind tunnel is investigated by compressible wall-resolved large-eddy simulations possibly coupled with the Ffowcs-Williams and Hawkings acoustic analogy. The numerical domain includes the nozzle and the anechoic chamber, which allows the direct taking of the installation effects into account. The simulated span (25% of the flap chord) is the largest one simulated so far for this configuration and, more generally, at this high Reynolds number. The results of the simulation are validated with the extensive experimental database for the chosen configuration. A good overall agreement with experimental data is achieved for all mean and fluctuating velocities, as well as wall pressures on the wing and the flap, especially the power spectral densities, the convection velocities, and even the streamwise and spanwise coherences on both elements. Similar good predictions of the far-field acoustic pressure using a hybrid approach are achieved, although the acoustic analogy does not allow taking into account the jet noise given that the Ffowcs-Williams and Hawkings surfaces are placed within the jet core. The acoustic results obtained with the acoustic analogy are also compared with the numerical microphones placed in the far field, showing a good agreement up to the mesh cut-ff frequency. The dilatation field and the sound directivity stress that the flap and wing trailing edges are the dominant noise sources of the wing-flap configuration, with significant diffraction effects on the flap side. Evidence of slight boundary-layer instabilities is also shown close to the flap trailing edge.