Search

International audience; This paper is aimed to present a computational chain developed in the framework of the CleanSky 2 European CONCERTO project. This computational chain is devoted to the prediction of the noise emitted by the lateral rotors of the Airbus Helicopters' RACER demonstrator using both fast prediction and high fidelity approaches. One of the main challenges addressed in this paper is the capacity to predict rapidly the aerodynamic and acoustic interaction effects due to the vicinity of the wings and the fuselage. From an aerodynamic point of view, it is proven by comparison with high-fidelity results that it can be achieved thanks to a free-wake code using velocity perturbation fields to properly take into account the wings wake viscosity effect and to solve issues linked to the rotational speed difference between the main rotor and the propellers. Comparisons with a Boundary Element Method code show also that a Kirchhoff approximation appears to be a good option to rapidly assess, at least in terms of tendencies, the impact of near solid surfaces on the noise radiation.

Recent innovative engine integration systems present interesting prospects for considerable aircraft fuel burn reduction. In this context, the Airbus Nautilius is a patented engine integration concept embedding two Ultra High Bypass Ratio (UHBR) turbofans at the rear of the fuselage so as to take the full benefit of the boundary layer ingestion (BLI). This concept presents very promising power savings compared to classical podded configurations when neglecting the penalty on fan performance. However, as the engine is now working in distorted boundary layer flow conditions, these benefits can be partially offset by an additional fan performance penalty. In order to assess these additional losses and therefore to refine the potential of this concept, a numerical fan design activity has been conducted by Onera on behalf of and in collaboration with Airbus. First, blade design modifications have been applied to a pre-existing UHBR fan stage originally designed for “classical” podded configurations in order to maximize the isentropic efficiency in cruise conditions. The results of this first activity shows that more than half of the fan isentropic efficiency penalty due to the distortion at the engine inlet can be recovered by few design iterations. Secondly, an operability assessment at take-off high-lift conditions has been conducted on the optimized geometry and ensures that the fan stall margin remains acceptable. In conclusion, these results confirm the initial potential and mark an additional step towards a broader assessment of the Nautilius engine integration concept, which shall be further completed by acoustic and aeroelastic studies.

International audience; Experimental measurements, steady (RANS) and unsteady (URANS) numerical simulations are performed on a 3.5:1 prolate spheroid at angles of attack from 0° to 90°. The Reynolds number considered is ReL=2.57*1^6, corresponding to the wind tunnel conditions. CFD simulations are performed with OpenFOAM, using the k-omega SST and the Spalart-Allmaras turbulence models. Analyses of aerodynamic coefficients and surface pressure show a good agreement between CFD simulations and experimental results. The turbulent structures in the wake of the spheroid have a complex topology, strongly dependent on the angle of attack considered. Results of URANS simulations allow to identify turbulent structures that are steady and asymmetric at low angles of attack, symmetric and unsteady at higher values. The configuration at AoA=90° is the most complex with the presence of disorganized and unstable structures.