Aeroacoustic Study of a High-Fidelity Aircraft Model: Part 1-Steady Aerodynamic Measurements

20th AIAA/CEAS Aeroacoustics Conference

Humphreys

Lockard

et al. 2014

Aeroacoustic measurements for a semi-span, 18% scale, high-fidelity Gulfstream aircraft model are presented. The model was used as a test bed to conduct detailed studies of flap and main landing gear noise sources and to determine the effectiveness of numerous noise mitigation concepts. Using a traversing microphone array in the flyover direction, an extensive set of acoustic data was obtained in the NASA Langley Research Center 14-by 22-Foot Subsonic Tunnel with the facility in the acoustically treated openwall (jet) mode. Most of the information was acquired with the model in a landing configuration with the flap deflected 39º and the main landing gear alternately installed and removed. Data were obtained at Mach numbers of 0.16, 0.20, and 0.24 over directivity angles between 56º and 116º, with 90º representing the overhead direction. Measured acoustic spectra showed that several of the tested flap noise reduction concepts decrease the sound pressure levels by 2 -4 dB over the entire frequency range at all directivity angles. Slightly lower levels of noise reduction from the main landing gear were obtained through the simultaneous application of various gear devices. Measured aerodynamic forces indicated that the tested gear/flap noise abatement technologies have a negligible impact on the aerodynamic performance of the aircraft model.

Section: Gear-flap Interaction Noisementioning

confidence: 91%

Aeroacoustic Evaluation of Flap and Landing Gear Noise Reduction Concepts

20th AIAA/CEAS Aeroacoustics Conference

Humphreys

Lockard

et al. 2014

“…Figures 2 and 3, reproduced from Ref. 9, show the top view of the spanwise location and numbering of the static pressure rows on the model wing, winglet, and flap. Note in Fig.…”

Section: Simulated Model Geometrymentioning

confidence: 99%

“…The initial entry, completed in November 2010, focused on acquiring global forces (lift and drag) and measurements of steady and unsteady surface pressures. Detailed accounts of that entry and the processed aerodynamic data are given in Khorrami et al 9 and Khorrami and Neuhart. 10 The second 14x22 tunnel entry was executed in two segments.…”

Section: Introductionmentioning

confidence: 99%

Towards Full Aircraft Airframe Noise Prediction: Lattice Boltzmann Simulations

20th AIAA/CEAS Aeroacoustics Conference

Fares²,

Casalino³

2014

Computational results for an 18%-scale, semi-span Gulfstream aircraft model are presented. Exa Corporation's lattice Boltzmann PowerFLOW® solver was used to perform time-dependent simulations of the flow field associated with this high-fidelity aircraft model. The simulations were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39º (landing configuration). We focused on accurately predicting the prominent noise sources at the flap tips and main landing gear for the two baseline configurations, namely, landing flap setting without and with gear deployed. Capitalizing on the inherently transient nature of the lattice Boltzmann formulation, the complex time-dependent flow features associated with the flap were resolved very accurately and efficiently. To properly simulate the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips. Extensive comparison of the computed time-averaged and unsteady surface pressures with wind tunnel measurements showed excellent agreement for the global aerodynamic characteristics and the local flow field at the flap inboard and outboard tips and the main landing gear. In particular, the computed fluctuating surface pressure field for the flap agreed well with the measurements in both amplitude and frequency content, indicating that the prominent airframe noise sources at the tips were captured successfully. Gear-flap interaction effects were remarkably well predicted and were shown to affect only the inboard flap tip, altering the steady and unsteady pressure fields in that region. The simulated farfield noise spectra for both baseline configurations, obtained using a Ffowcs-Williams and Hawkings acoustic analogy approach, were shown to be in close agreement with measured values. NomenclatureAOA = angle-of-attack C L = lift coefficient Cp' rms = unsteady RMS pressure coefficient Cp = pressure coefficient c = local chord DNS = Direct Numerical Simulation DES = Detached Eddy Simulation MDDES = Modified Delayed Detached Eddy Simulation GAC = Gulfstream Aerospace Corporation Hz = Hertz, cycles per second LES = Large Eddy Simulation M = Mach number PSD = power spectral density in [psi 2 /Hz] or [dB/Hz] psi = pounds per square inch Re = Reynolds number RMS = root mean square * Aerospace Engineer, Computational AeroSciences Branch, Associate Fellow AIAA AIAA 2014-2481 AIAA Aviation 2 RNG = Re-Normalization Group s = second URANS = unsteady Reynolds averaged Navier-Stokes VR = variable resolution X, Y, Z = right handed coordinate system

“…A detailed description of this model is provided in Ref. 9. The noise reduction concepts presented in this paper represent only a subset of those that were simulated prior to testing on the semi-span model in the 14x22 tunnel.…”

Section: Baseline Model Geometry and Noise Reduction Conceptsmentioning

confidence: 99%

“…Several earlier papers document the steady 9 and unsteady 10 measurements of the baseline configuration as well as the aerodynamic 11 and aeroacoustic 12 performance of the noise reduction concepts.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Airframe Noise Reduction Concepts via Simulations Using a Lattice Boltzmann Approach

Fares¹,

Casalino²,

21st AIAA/CEAS Aeroacoustics Conference

2015

Unsteady computations are presented for a high-fidelity, 18% scale, semi-span Gulfstream aircraft model in landing configuration, i.e. flap deflected at 39° and main landing gear deployed. The simulations employ the lattice Boltzmann solver PowerFLOW® to simultaneously capture the flow physics and acoustics in the near field. Sound propagation to the far field is obtained using a Ffowcs Williams and Hawkings acoustic analogy approach. In addition to the baseline geometry, which was presented previously, various noise reduction concepts for the flap and main landing gear are simulated. In particular, care is taken to fully resolve the complex geometrical details associated with these concepts in order to capture the resulting intricate local flow field thus enabling accurate prediction of their acoustic behavior. To determine aeroacoustic performance, the farfield noise predicted with the concepts applied is compared to high-fidelity simulations of the untreated baseline configurations. To assess the accuracy of the computed results, the aerodynamic and aeroacoustic impact of the noise reduction concepts is evaluated numerically and compared to experimental results for the same model. The trends and effectiveness of the simulated noise reduction concepts compare well with measured values and demonstrate that the computational approach is capable of capturing the primary effects of the acoustic treatment on a full aircraft model.