G. Redeker, R. Müller, A. Blanchard, J. Reneaux

In a DLR-ONERA cooperation the transonic laminar airfoil DLR - LV2 was tested in the T2 wind tunnel of ONERA/CERT, Toulouse. Although the airfoil design is dedicated to a swept NLF wing the airfoil was tested under unswept conditions allowing laminar boundary layers to be maintained up to 60% of airfoil chord, where transition is provoked by TS-instability. Tests were carried out at ambient and cryogenic temperatures at Re = 3.3 x 10^6 to 10 x 10^6 in the range of M = 0.72 to 0.76, measuring pressure distributions, airfoil wakes and surface temperatures. From these measurements the aerodynamic coefficients and the transition location could be evaluated by a certain increase in the heat transfer coefficient determined by surf ace temperature differences. The measured polars showed remarkable laminar drag buckets with lowest drag coefficients of cD=0.0038. At the upper limit of the drag bucket a strange behaviour of cD could be observed which leads to an increase of cD followed by a certain decrease again. This behaviour could be explained by the movement of the transition location on the upper surface in interaction with the development of the pressure distribution in the supersonic region. This was checked by stability analysis and limiting N-values of N=14 (incompressible code SALLY) and N=7 (compressible code Arnall have been reached. Tests at higher Reynolds numbers Re > 10^6 exhibit disturbances in the laminar boundary layer due to ice particles in the flow at temperatures below 170K. Computations of data points revealed an excellent agreement in aerodynamic coefficients as well as in pressure distribution, indicating that the T2 wind tunnel results are nearly wall interference free.

First European Forum on Laminar Flow Technology, Hamburg, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 11 Seiten

DGLR-Bericht, 1992, 1992-06, First European Forum on Laminar Flow Technology; S.141-151; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aerodynamics, boundary layer transition, laminar flow

Bestellbar

1992