Abstr:RAE M2155 Wing
Application Area 1: External Aerodynamics
Application Challenge AC1-02
The wing RAE M2155 is a low aspect-ratio (3.27) swept wing that has been tested at the DERA 8ft x 6ft transonic wind tunnel in the Mach number range 0.6 - 0.87. The wing was mounted directly on the wall of the tunnel, so that the wall boundary layer and wing boundary layer interact. Tunnel wall interference effects have been measured, and were found to be significant especially for the higher Mach number test conditions. The computational studies, therefore have been performed as internal flow calculations, making tunnel corrections unnecessary.
At the design conditions (Mach number 0.86, lift coefficient 0.5, Reynolds number 4x106, based on geometric mean chord) the wing has the following characteristics: attached boundary layer everywhere; high rear loading, providing a difficult test of the calculation of boundary layer growth; and a triple shock structure on the upper surface. At off design conditions, flow separations occur.
Wing and tunnel wall pressure measurements are available for several combinations of Mach number and incidences. A set of 4 conditions (named as case 1-4) have also oil flow pictures, boundary layer measurements, and skin friction coefficient. Normal force coefficients have been calculated from the measured pressure distribution at several span stations and integrated on the whole wing.
The wing RAE M2155 has been the subject of many numerical simulations, and has been chosen to validate and assess turbulence models in E.C. funded project AVTAC.
Computations have been performed at QINETIQ for the case 1,2,3, and 4 by using the following turbulence models :
- A κ-g based variant of the Menter SST scheme
- A κ-g based EARSM utilizing a novel calibration and incorporating explicitly the variable ratio of turbulence production to dissipation rate.
- A tensorially linear version of the κ-g based EARSM model (only case 3).
and at CIRA, for the case 2, by employing the following turbulence models :
- Myong-Kasagi κ-ε
- Non-Linear κ-ε (Myong-Kasagi κ-ε + 2nd order constitutive relation by Shih)
- Standard Wilcox κ-ω
- Kok TNT κ-ω
- Menter SST κ-ω
The numerical results consist of pressure and skin friction coefficients as well as velocity profiles at several stations along the wing span.
The M2155 test cases were specifically intended for the validation of CFD methods, as aeronautical design tools. The test geometry, consisting of a wing attached to a wind-tunnel wall, is akin to a wing-body configuration, although the test flow is clearly an internal one. The importance of such configurations for aeronautical applications is obvious. The wing is swept and is of low aspect ratio, as is common in military applications. The low aspect ratio of the wing ensures that the resulting flow is strongly three-dimensional. Inappropriate modeling in the wing-wall junction, for instance, can affect the computed flow over a significant fraction of the span. The wing design and test conditions probe the buffet and separation boundaries at the edge of the flight envelope, these boundaries being of importance in both civil and military aircraft design, and providing a considerable challenge to numerical flow solvers. The flows are complex with three-dimensional separations and triple shock structures. The boundary layers are subjected to strong adverse pressure gradients (the trailing edges being heavily loaded), a regime which is difficult for numerical methods but of great importance in wing design.
The simulation of this kind of flow represents a severe and relevant test to assess the ability of the computational methods. The prediction of the shock waves system, of the separation and reattachment lines and of the pressure recovery behind the shock and in the trailing edge zone are the challenges for the turbulence models.
The design and assessment parameter are the aerodynamic coefficients.
Normal force coefficients have been calculated from the measured pressure distributions and integrated on the whole wing. It is therefore possible to determine inviscid values of the aerodynamic coefficients.
Contributors: Pietro Catalano - CIRA; QinetiQ