Reynolds Number Scaling Effects on the European High-Lift Configurations

Abstract

Within the European High-Lift projects I and II, extensive experimental and numerical investigations on the aerodynamics of high-lift configurations have been carried out. The studies are conducted using the KH3Y windtunnel model DLR F11, which is representative of a wide-body commercial aircraft. A step-by-step complexity increase up to a complete high-lift configuration, including pylon, nacelle, and nacelle strake, is carried out to identify and separate the lift and drag behavior for the components of the high-lift system and their Reynolds number dependency. The wind-tunnel data have been gathered in the European Transonic Wind Tunnel in Cologne in three different test campaigns. To include the complete analysis of the stall behavior for the different configurations of a complex three-dimensional tapered high-lift wing with nacelles extends the scope of a single paper. Therefore, the focus of the present contribution is laid on the detailed analysis of Reynolds number scaling effects with respect to lift curves and drag polars. The combined variation of the dynamic pressure and the total temperature in the European Transonic Wind Tunnel allows covering a Reynolds number range from Re 1:5 10 6 up to deep cryogenic conditions with Re 25 10 6. The final comparison of the four configurations reveals that the sequence of maximum lift values is maintained for the lowest and highest Reynolds number, although the increments between the configurations differ. The strongest increase in maximum lift is observed up to Re 5 10 6. In the intermediate range, 5 10 6 < Re < 15 10 6 , a highly nonlinear behavior of the maximum-lift values is observed, which requires further investigation.

Estimation of Aerodynamic Coefficients in a Small Subsonic Wind Tunnel

“…To calculate the second member in Equation 14, the increase of axial coefficient due to model support interferences, it is necessary to measure the pressure C pr in the ring between the hole and sting. In this paper, for prediction purposes only, the influence of the sting on this pressure is neglected and used as C pb =C pr =-0.12, according to literature [9]. For the sting diameter of 10 mm, it follows that S S =78.5 mm 2 , and if the cross section diameter is 12 mm, S 0x =113 mm 2 .…”

“…The aerodynamic coefficients of the airplane in cruise ( Figure 3) without a sideslip angle are axial force along x axis, C A and normal force along z axis, C N [9]:…”

“…The dependency of the aerodynamic properties on the Reynolds number is a typical example of the socalled Reynolds number scaling effects, which play an important role when results from subscale wind-tunnel tests must be extrapolated to flight conditions [9].…”

Comparison of Octree and Omni-Tree Cartesian Grid for Civil-Plane High-Lift Model Simulations

“…On the other hand, to reduce the wind-tunnel test costs and the design cycle time, some significant efforts are now underway with the development of computational fluid dynamics (CFD) techniques for the prediction of high-lift flowfields [3][4][5][6][7]. In this paper, emphasis is placed on the grid generation method.…”

“…Our goals are to modify the original octree Cartesian grid method through the use of an omni-tree data structure, so as to highlight the prominent changes in the grid generation of the numerical simulation of flowfield over high-lift configuration. In contrast to the previous studies that concentrate on a single solution approach, such as the multi-block grid method in [5], the chimera technique in [6], or the hybrid unstructured approach in [7], the present work offers the possibility of extending the applications and capabilities of the Cartesian grid method.…”