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International audience; In the SWAHILI (SWept Airfoil with HIgh LIft) Onera-DLR Common Research Project (CRP), both research centers are building an experimental database for the validation of CFD/CAA codes applied to the simulation of the unsteady flow and noise generation from a high-lift profile with deployed slat and flap and a global sweep angle of 30°. The project is based on DLR’s model F16, a two-dimensional airfoil (constant section in the span direction), with a 300 mm clean (retracted) chord. This project is a continuation of the LEISA2 (Silent Take-Off and Landing, 2010-2013) project, in which a similar database has been built with the same model, but without sweep angle. Since 2014, the LEISA2 test-case has been included by NASA and AIAA in the Benchmark for Airframe Noise Computations (BANC). In both projects LEISA2 and SWAHILI, the model has been tested in F2, an aerodynamic wind tunnel located in Onera-Le Fauga, with intensive aerodynamic measurements, including steady/unsteady wall pressure sensors, optical devices such as PIV and steady/unsteady LDV and a hot wire probe. Acoustic measurements were also achieved in F2 with a wall microphone array mounted in the windtunnel ceiling. During the SWAHILI project, Dassault-Aviation has partnered with Onera and DLR, contributing to the project with two additional configurations of flap side edge, with the same aerodynamic and acoustic measurements in F2. In LEISA2 the un-swept model has been also tested in AWB, an anechoic open-jet wind tunnel located in DLR-Braunschweig for acoustic data acquisition. In the SWAHILI context, similar tests are under progress with the SWAHILI swept model. The present paper focusses on the influence of the sweep angle and the flap side edge on the characteristics of the unsteady flow and on the radiated noise.

This paper presents numerical flow predictions of a two-wheel landing gear. Computations are based on the Lattice Boltzmann Method implemented in LaBS, a solver developed by a French consortium led by industrial companies and academic institutes. The landing gear geometry is one of the LEG (“Landing gear noise Evaluation Geometry ”) landing gear model configurations designed and tested by JAXA. This model includes geometric details such as the wheel-caps with cooling holes, brake calipers, and torque link. The unsteady flow simulations are achieved on “octree” Cartesian grids using cubic cells with refinement doubled along surfaces assigned by the user. Solid surfaces are treated via an Immersed Boundary Method. Two computations are currently achieved on grids with coarse and medium resolutions, and a final computation on a fine grid is still running. The time-averaged wall pressure on the wheels and velocity components in the landing gear wake show a global agreement with the steady pressure taps and PIV respectively. The main discrepancies appears in the flow deviation because the boundary conditions of the flowdiffers from open-jet condition in CFD to closed-test section in wind-tunnel. The medium grid compuations globally improves the time-averaged and unsteady aerodynamic predictions regarding the coarse grid results. Given their accuracy, these results already confirms the relevancy of the lattice-Boltzmann method for the landing-gear flow simulation., Cet article présente les prévisions numériques du bruit d'un train d'atterrissage à deux roues.Les calculs sont basés sur la méthode Lattice Boltzmann implémentée dans LaBS, un solveur développé par un consortium français dirigé par des entreprises industrielles et des instituts universitaires. La géométrie du train d'atterrissage LEG est un modèle de train d'atterrissage conçu et testé par la JAXA. Ce modèle comprend des détails géométriques tels que les jantes des roue avec des trous de refroidissement, des éléments de freinage et un compas. Les simulations d'écoulement instationnaire sont réalisées sur des grilles cartésiennes dites "octree" utilisant des cellules cubiques avec un raffinement doublé le long des surfaces assignées par l'utilisateur. Les surfaces solides sont traitées par une méthode des frontières immergées. Deux calculs sont actuellement effectués sur des résolutions grossières et moyennes, et un calcul final sur une grille fine est toujours en cours. La pression moyenne sur les roues et les composantes de vitesse dans le sillage du train d'atterrissage montrent un accord global avec les mesures réalisées en soufflerie. Ces résultats, bien que limité à un maillage de taille moyenne, confirme l'intérêt de la méthode LBM pour la simulation d'écoulement de train d'atterrissage.

In the context of the evaluation and reduction of fan noise in modern turbofan engines, the possibility to compute the acoustic transmission through a rotor-stator system, accounting for the rotation of the rotor, is evaluated. The objective is the development of a numerical method to simulate the propagation of acoustic waves in a global fixed region which includes a partial moving zone, with equations solved in a fixed reference frame. In order to insure a high order resolution these CAA developments and computations were performed using Onera’s CAA solver sAbrinA-V0. Firstly, a full or partial 2D moving zone was employed as a reference test case. It was insured that the moving grid acts only as a resolution support and does not affect the propagation of the waves by its rotation. Monopole and planar sources were considered. In order to connect the two (fixed and rotating) zones, spline cubic interpolation functions were employed in the ghost cells rows. Secondly, a cross-shaped rigid obstacle with zero thickness walls was embedded in the moving grid and the interaction between this obstacle and a fixed monopole was computed. Note that, despite the CAA solver can handle any non-homogeneous mean flow, this case was addressed accounting for a medium at rest. The field of application of the method is restricted to non-viscous interactions between boundary layer and acoustics, so the considered mean flows have to respect this condition. Finally, a 3D test case is presented, based on a simplified rotor with four twisted blades with zero thickness in a perfect annular duct. The acoustic interaction of this rotating blades with an helicoidal modal source injected upstream the rotor within a medium at rest was evaluated. Recent developments in sAbrinA-v0 on improved inlet/outlet acoustic boundary conditions and conclusions of gust-fixed airfoil interactions will allow a proper evaluation of CAA simulations of moving surfaces.