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This paper presents the outcome of numerical simulations of the flow field inside the ONERA F1 wind-tunnel, which is a large-scale pressurized low-speed wind tunnel mostly used to investigate the take-off and landing performance of aircrafts in high-lift configuration. The simulations were carried out under RANS modelling assumptions. Results were compared to available experimental data characterizing the tunnel flow-field, especially in the test section. The overall flow physics is well captured by the simulations. However, when looking at the result with a more demanding level of accuracy, some important characteristics of the velocity distribution in the test section, such as flow upwash and total pressure distribution, are not replicated. Reasons are discussed in the paper, and some recommendations are derived for future similar simulations., Cet article présente les résultats de simulations numériques de l'écoulement dans la soufflerie F1 de l'ONERA, qui est une grande soufflerie subsonique pressurisée, principalement utilisée pour étudier les performances des avions en configuration hypersustentée, lors des phases de décollage et d’atterrissage. Les simulations ont été menées avec une modélisation RANS. Les résultats sont comparés aux données expérimentales disponibles pour caractériser l'écoulement, en particulier dans la veine d'essai. Les principaux phénomènes physiques sont bien reproduits par les simulations. Toutefois, si l'on regarde les résultats avec une exigence de précision supérieure, certaines caractéristiques importantes de l'écoulement dans la veine, comme la répartition d'ascendance et de pression totale, ne sont pas reproduites. L'article en discute les raisons et émet des recommandations pour de futures simulations semblables.

International audience; Spatial linear stability analyses are performed in order to study laminar-turbulent transition in the boundary layer on the Z49 rotor, rotating in a Ma = 0.75 freestream. In a rotating reference frame, terms corresponding to Coriolis and centrifugal forces appear in the linearized disturbance equations. However, the effect of these rotational terms on the stability of laminar boundary layers is only partially understood. The rotational terms' impact on the transition mechanisms is studied by neglecting or considering rotation in the linear local stability and parabolized stability equations. The present results show that rotation hardly affects the instability characteristics of Tollmien-Schlichting waves. On the other hand, rotation destabilizes the cross-flow instabilities, but not enough to trigger cross-flow-dominated transition at the investigated operating condition.

International audience; This papers points out some weaknesses of the solution-adapted process. They have been solved by improving the Newton's method of the flow solver enabling convergence to machine zero at each run of the solution adaptive process. This work also presents the benefits of using metric-based anisotropic mesh adaptation for the numerical simulation of high lift configurations. For instance, we reconsider the CRM-HL geometry of the 3rd AIAA CFD High Lift Prediction Workshop and we obtain a prediction of the lift value similar to that of the x-fine mesh generated with the best practices (206 million vertices) with an adapted mesh composed only of 2.7 million vertices. This represents a reduction in the mesh size by a factor of 75.

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.

The numerical prediction of mass transfer rates of gas components within the liquid phase in a stirred two-phase flow reactor is presented. Experiments have been conducted to determine the flow regime and the number and sizes of the bubbles formed under different conditions. The dynamic field of the two-phase flow was obtained through numerical simulations. Bubbles with the experimentally measured diameter were released from the free surface and tracked numerically to compute the particle Reynolds number, which is used to determine the mass transfer rates. The unbaffled reactor provides mass transfer rates 30% larger than the baffled reactor for the bubbly flow. Mass transfer rates drop about 65% when the emulsion is formed. Therefore, above the critical rotation rate at which the emulsion forms for the unbaffled reactor, the baffled configuration provides larger mass transfer rates. The results indicate that even for the most unfavorable case mass transfer is not the limiting step, as 90% of the equilibrium concentration is reached in 10 s.

Computational Fluid Dynamics (CFD) has been used to simulate the application of pesticides on a vineyard by using an air-assisted sprayer. The selected sprayer, inverted u-shaped, consisted of vertical ducts, facing the crop hedge, through which the air generated by a turbine came out, transporting the pulverized drops until its deposition on the crop. Considering this air-assisted sprayer, CFD modelling has been used to develop a dispersed model including both, liquid and air phases, with the goal of analysing the effects of the main setting parameters of the sprayer: liquid flow, droplet size, air flow and forward speed.

Technology is advancing at a rate that makes it extremely difficult for the mining industry to keep pace. Many advances occur within a given piece of technology and often this is missed by the disciplines that could have gained advantage by its implementation. Often this may have been simply an aspect of cost exceeding benefit. However, there are some technologies that potentially have such a far-reaching impact on the mining industry that the benefits simply outweigh the cost. The application of 3D laser scanning in the mining industry has the potential of taking the concept of 'Google mapsTM' underground. This presents an opportunity where the virtual world of underground can be traversed with relative ease and many aspects of measurements could be obtained without having to visit the working place again, potentially saving countless man-hours and still delivering precision work with significant savings in downtime, stoppages, and exposure to safety incidents. Anglo American Platinum maintains its competitive advantage though the review and application of appropriate technology. This paper describes the 3D laser scanning trial at one of Anglo American Platinum's new shafts, and goes on to show the benefits encountered through the application and the involvement of the various MRM disciplines.