Design of a Swept-Wing Laminar Flow Control Flight Experiment for Transonic Aircraft

This paper addresses the conceptual design of a flight-test experiment incorporating a laminar flow control (LFC) wing glove on a business-jet-type aircraft. These experiments are designed to extend the spanwise periodic discrete roughness element (DRE) technology to chord Reynolds numbers between 15-20 million at a unit Reynolds number of 1.6 million per foot. A number of key questions were addressed and it is shown that: (1) it is possible to find an aircraft that can be used as a platform for this experiment and the selection converged on the Gulfstream II (G-II) based on suitability and expected availability; (2) a CFD of the aircraft flowfield showed that there is no interference from engines that would compromise the experiment. A computational grid for the G-II was created, and engine nacelle effects are “accountable” in the outboard section and the flowfield is spanwise-uniform where the glove would be located. Also, streamline deflections are accountable including AoA and inplane deflection effects on the glove; and (3) it is possible to design an airfoil with a representative C l and C p distribution making DREs feasible. An airfoil section was designed that suggests NLF (natural laminar flow) is possible at AoA = 0°, with potential for DRE control between AoA = -0.5 and -1°.

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