Simulations of a Full-Scale Aircraft with Installed Airframe Noise Reduction Technologies

Abstract

Computational results are presented for a high-fidelity, full-scale, full-span Gulfstream G-III aircraft model equipped with flap and main landing gear (MLG) noise reduction technologies. The simulations, which were conducted in support of a NASA airframe noise flight test campaign of the same technologies, use the lattice Boltzmann solver PowerFLOW ® to capture time-accurate flow data with sound propagation to the far field accomplished using a Ffowcs-Williams and Hawkings (FWH) acoustic analogy approach. The aerodynamic and aeroacoustic behavior of the aircraft were investigated in the approach configuration with combinations of flap and landing gear deployments. The simulated flap concept is an Adaptive Compliant Trailing Edge (ACTE) flap that replaces the Fowler flap system on the G-III aircraft. The simulated MLG noise reduction concept is comprised of porous fairings and a collection of other smaller fairings fitted around the flow-facing components. Using the Fowler flap results as a reference, comparisons are presented on the noise reduction effectiveness of the ACTE flap system. Investigations were made on the effects of using the porous fairings and ACTE flap as noise reduction concepts in tandem. The ACTE flap was found to reduce the total airframe noise level at all flap deflection angles when compared to the Fowler flap equipped model. As anticipated, a reduction in aerodynamic performance was also found when the ACTE flap system was used. The MLG fairings were shown to further reduce the total airframe noise level of the G-III.

Numerical Wire Mesh Model for the Simulation of Noise-Reduction Devices

“…For that reason, it is very difficult to directly simulate them in actual computations, although some teams report unsteady simulations of the flow around landing gear with porous fairings [4,7], for a high computational cost. For instance, the lattice-Boltzmann very largeeddy simulation of Ferris et al [7] required the explicit discretization of about 11,000 holes with diameters of 2 mm in the porous knee fairing placed around the main landing gear of the full-scale NASA Gulfstream G-III aircraft. Although such simulations are very useful for flow physics analysis, they cannot be considered as an option for porous fairing optimization at the present time.…”

“…5) The target values of ρ T , u i;T , p T , and νT are then locally imposed to all corrected points, at each time step, by the use of the source terms [Eqs. (4)(5)(6)(7)] in the modified Navier-Stokes equations, as was done for the wall model (see Sec. II).…”

Numerical Simulations of a Landing Gear with Flow Through Fairings for Noise Mitigation

“…This makes their direct resolution almost impossible to perform, due to computational limitations, or at the expanse of large computational grids, e.g. [10]. Therefore, dedicated macroscopic numerical models have to be developed and validated.…”