Inverse Airfoil Design via Specification of the Boundary-Layer Transition Curve

Abstract

In a general sense, inverse airfoil design can be described as the means by which desired aerodynamic characteristics along with certain geometric constraints are specified and the resulting airfoil shape that satisfies the specifications is determined. In this paper, an approach is presented in which an airfoil can be designed by specifying the boundary-layer transition curve. By specifying the transition curve, the desired airfoil performance can be more readily achieved by taking advantage of the strong relationship between the boundary-layer transition curve and the drag polar. This approach builds on the inverse design method, PROFOIL. This paper contains a brief description of the PROFOIL code as well as an overview and a detailed formulation of the current approach. In the approach, a multidimensional Newton iteration scheme is used to adjust the velocity distribution over a segment of the airfoil until the transition lift coefficient is within a specified tolerance. This paper also contains examples demonstrating both the validity and usefulness of this method. The ability to specify the transition curve represents as enhancement over existing single and multipoint design methods in that the current approach allows for a single specification that spans multiple operating points.