Aeroacoustic Simulation of a Nose Landing Gear in an Open Jet Facility using FUN3D

Abstract

Numerical simulations have been performed for a partially-dressed, cavity-closed nose landing gear configuration that was tested in NASA Langley's closed-wall Basic Aerodynamic Research Tunnel (BART) and in the University of Florida's open-jet acoustic facility known as UFAFF. The unstructured-grid flow solver, FUN3D, developed at NASA Langley Research center is used to compute the unsteady flow field for this configuration. A hybrid Reynolds-averaged Navier-Stokes/large eddy simulation (RANS/LES) turbulence model is used for these computations. Time-averaged and instantaneous solutions compare favorably with the measured data. Unsteady flowfield data obtained from the FUN3D code are used as input to a Ffowcs Williams-Hawkings noise propagation code to compute the sound pressure levels at microphones placed in the farfield. Significant improvement in predicted noise levels is obtained when the flowfield data from the open jet UFAFF simulations is used as compared to the case using flowfield data from the closed-wall BART configuration.

Aeroacoustic Simulation of Nose Landing Gear on Adaptive Unstructured Grids with FUN3D

“…For the 58 million node grid, the computed results are qualitatively similar to the measured data and the 145 million node results from Ref. 7, and display the correct shape and trends for the decay of TKE levels in the wheel wake and shear layer regions.…”

“…Computational results for this configuration obtained on a custom-enriched grid consisting of 145 million nodes were shown by Vatsa et al 7 to compare well with measured steady and perturbation pressure data, as well as with farfield noise data. This 145 million node grid is designated as "reference grid" in this paper.…”

“…Solutions based on the 145 million node grid from Ref. 7, and the experimental data are also shown in this figure. The agreement of computed pressures with the experimental data improves with grid refinement, the biggest gain seen by going from 18 to 40 million nodes.…”

“…The computational results from the 145 million node grid of Ref. 7 are also plotted in these figures for reference. Even though the surface grids are identical for the 18, 40 and 58 million node grids, a gradual improvement in agreement with the experimental data is observed with adaptive grid refinement.…”

“…5 The FUN3D code has also been used to solve the flow over landing gear configurations and resulting solutions on enriched unstructured grids were shown to compare well with experimental data. 6,7 However, generation of such hand-tuned enriched grids requires significant human effort, intuition and a priori knowledge of the flow field.…”