The LAGOON program currently supported by Airbus Operation SAS and involving ONERA and DLR (the French and German national aerospace research centres) and Southampton University, focus on the validation of aeroacoustics numerical tools for landing gear applications. An experimental aeroacoustic program have been performed in ONERA's aerodynamic and anechoic windtunnels F2 and CEPRA19 with a generic landing gear configuration. The present work follows the previous CFD/CAA coupling of the baseline landing gear model configuration at Mach number M = 0.23. Using the same computational process but run at a Mach number M = 0.18, CFD is achieved with Zonal-Detached Eddy Simulation (ZDES) using ONERA's code elsA and provides the data for the FfowcsWilliams and Hawkings surface integral methods (Onera's code KIM). Both solid and porous surfaces are used and compared to experiment. In addition, the errors probably induced by the acoustic reflections on the CFD floor and the wake impinging the porous surfaces are studied. These errors are found to be minimal in the upstream direction where the porous surface results are in best agreement with experiment. In all directions, the solid surface results are in good agreement with experiment, predicting an overall sound pressure level with an error lower than 1.5 dB.
This paper is part of ONERA's effort to compute the noise generation around landing gears, effort that has been shown with studies on a variety of configurations such as the ones included inside the BANC-II (Benchmark problems for Airframe Noise Computations). In this case, the addressed geometry is the LAGOON baseline nose landing gear. On the present computation, a refined unstructured mesh is generated for resolving the boundary layer up to y + around one. The simulation of the flow was performed using a Zonal Detached Eddy Simulation (ZDES) model, implemented inside ONERA's code CEDRE. The transient data obtained were used as input for a Ffowcs-Williams and Hawkings computation over the skin of the landing gear and on a porous surface around it, which was performed using ONERA's in-house code KIM. Both the aerodynamic and aeroacoustic results are compared with the experimental ones obtained at F2 and CEPRA19 test campaigns. The comparisons obtained show a good agreement in terms of mean field, wall pressure (mean and spectral content) and aeroacoustic far-field measurements. Nomenclature LG= Landing Gear r d = Generic parameter in DDES CFD = Computational Fluid Dynamics ν = Molecular viscosity CAA = Computational Aero Acoustics ν t = Kinematic eddy viscosity ZDES = Zonal Detached Eddy Simulation k = Von Kármán constant M ∞ = Mach number d = Distance to the wall D = Wheel diameter ̂ = DDES shifting distance Re = Reynolds number U i,j = Velocity gradient dt = Time step Cp = Pressure coefficient CFL = Courant-Friedrichs-Lewy number FW-H = Ffowcs Williams and Hawkings Δ = Mesh size θ = Angular coordinate PIV = Particle Image Velocimetry U, V, W = Velocity comp. along X, Y and Z LDV = Laser Doppler Velocimetry RMS = Root-Mean-Square y + = Dimensionless wall distance MSD = Modeled Stress Depletion RANS = Reynolds-Averaged Navier-Stokes GIS = Grid Induced Separation C DES = Spalart's DES97 constant
The Aircraft Noise Working Group (ANSWr) was established by DLR, ONERA, and NASA to compare simulation tools, establish guidelines for noise prediction, and to assess uncertainties associated with the simulation. To accomplish these goals, a benchmark problem was initiated by the group. The setup is documented and initial results for the reference aircraft are discussed. The reference aircraft is a conventional tube-andwing configuration with the engines installed under the wings. The aircraft noise simulations are performed for departure and approach conditions, and the results obtained with three different system noise prediction tools are compared. At the aircraft level, the overall agreement is good between the three predictions. Peak noise levels agree within 3-4 dB. Fan and jet component predictions are generally very similar although there can be differences of up to 7 dB in some fan tone levels. The prediction of airframe components shows the most disagreement between the three methods with some differences of 6 dB for the major components and greater differences at high frequencies. There can also be differences in the frequency of the peak level and in the rank order of the airframe components. At the total airframe noise level, the differences are reduced to no more than 3-4 dB. While there is general agreement in shape characteristics of predicted ground noise isocontours, the differences between the three methods can result in more significant disagreement in the sizes of the isocontours.
International audienceThe flow features and acoustic emission of the two-wheel simplified LAGOON landing gear shallow cavity are numerically investigated. This cavity presents several differences when compared to other academic cases, the most important one is the flow detachment occurring before the cavity edge, generating a shear layer that develops over the cavity. Despite this difference, several agreements with academic studies of round cavities have been found in terms of incoming boundary layer characteristics, detached shear layer growth, and recirculation of the flow in the cavity. Furthermore a spectral analysis of the flow identified a vortex roll-up mechanism and its associated frequency in the shear layer. Finally the far-field noise emission of the cavity has been found to be broadband with the emergence of several narrow frequency contributions whose possible mechanisms of noise generation are discussed
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