Inverse Design of Adaptive Airfoils with Aircraft Performance Considerations

Abstract

Recent advances in the development of inverse airfoil design methods now allow for the incorporation of aircraft performance considerations in the design of a non-flapped airfoil. While these improvements make airfoil-aircraft matching considerably easier, there is a need for a similar capability for adaptive airfoils. This paper presents a design formulation that incorporates aircraft performance considerations in the inverse design of low-speed laminar-flow adaptive airfoils. The benefit of using adaptive airfoils is that the size of the low-drag region of the drag polar can be effectively increased without increasing the thickness of the airfoil. Two aircraft performance parameters are considered: level-flight maximum speed and maximum range. It is shown that the lift coefficient for the lower and upper corners of the airfoil low-drag range can be appropriately adjusted to tailor the airfoil for these two aircraft performance parameters. The design problem is posed as a part of a multidimensional Newton iteration in an existing conformal-mapping based inverse design code, PROFOIL. This formulation automatically adjusts the lift coefficients for the corners of the low-drag range for a given flap deflection as required for the airfoil-aircraft matching. Examples are presented to illustrate the benefits of the process for a general aviation aircraft and the results are validated by comparison with results from post-design aircraft performance computations.