A Theoretical Study of the Supercritical Aerofoil NLR 7301, and Comparison with Experiments.
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (ENGLAND)
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The aerofoil NLR 7301, 16.5 thick, was designed at NLR by their generalised hodograph method to give supercritical inviscid shock-free flow at the design condition free stream Mach number 0.72, lift coefficient 0.6. The paper describes a theoretical study of this aerofoil by the latest form of the RAE VGK method for calculating viscous effects in two-dimensional transonic flows. First, comparisons are given with experiments in the NLR Pilot Tunnel at a low Reynolds number 2.0 million per foot. Large discrepancies are shown near the design condition and at higher Mach numbers, which are ascribed to a laminar transitional shock waveboundary layer interaction in the transition-free experiments this causes an apparent weeakening of the shock wave and a spuriously low level of the measured drag. Next, calculations were made at two higher Reynolds numbers, with transition fixed near the leading edge 10 million, per foot to simulate conditions in a medium-sized wind tunnel and 50 million per foot, typical of full-scale conditions. Favourable scale effects are predicted on drag rise Mach numbers, for lift coefficient is greater than 0.5, and on separation onset at all life coefficients. It is concluded that the aerofoil should have an excellent performance at high Reynolds numbers. Author
- Fluid Mechanics