NLF Potential of Laminar Transonic Long Range Aircraft

Abstract

In this work we present analysis and design results of NLF airfoils and wings for long range aircraft. Extension of wing laminar boundary layer for long range transonic aircraft design is limited by large Reynolds numbers and large wing leading edge sweeps. To explore the NLF potential different swept tapered 2.75D airfoils were designed using the CATNLF method. CATNLF allows attenuating the crossflow instability amplification in the nose region for wings with long range sweeps and Reynolds numbers. Crossflow instability is reduced to a level so that in the nose region NLF is achieved without requiring suction. For 3D studies the long range NASA NLF common research model CRM-NLF is used. Stability analysis and further design is performed using the CRM-NLF wing geometry. Linear stability results obtained with the eN method for the 2.75D and 3D cases show that that theextent of laminar flow for regions downstream of the nose is strongly dependent on the used stability analysis approach. It is shown that using either incompressible or compressible stability analysis together with the currently used assumptions for critical flight N-factor values leads to a significant different potential of laminar extent and wave drag reduction possibilities.