CEAS 2015 paper no. 133 Page | 1 This work is licensed under the Creative Commons Attribution International License (CC BY). Copyright © 2015 by author(s). Aerodynamic Validation of a Parametric Airfoil Description TITEL Tomas Melin Fluid and Mechatronic Systems, Department of Management and Engineering, Linköping University Research Associate Linköping, SE-581 83, Sweden tomas.melin@liu.se Roland Gårdhagen Applied Thermodynamics & Fluid Mechanics, Department of Management and Engineering, Linköping University Assistant Professor Linköping, SE-581 83, Sweden roland.gardhagen@liu.se ABSTRACT This paper reports the aerodynamic validation of a parameterized modelling of wing profiles. The parameterization uses 4 piece-wise C1 continuous cubic Bézier curves to model the wing profile envelope. A large set of wing profiles were compared with respect to geometric and aerodynamic similarity between parametric model and point cloud representation. In particular boundary layer properties such as transition point position and drag coefficient; also the critical Mach number is compared between the two sets of wing profile modelling in order to support the conclusion that the two methods of geometrical representation are equivalent. 1 INTRODUCTION A fundamental part of aircraft design involves wing airfoil design and optimization, establishing an outer shape of the wing, which has good aerodynamic performance for the design mission, good internal volume distribution for fuel and systems and which also serves as an efficient structural member supporting the load of the weight of the aircraft. There are different methods for airfoil modelling used, depending on where in the design loop the work is done. In the conceptual phase a flat plate might suffice as wing profile model, while in later stages the airfoil might be selected from a database or being modifications of database airfoils. One key aspect of the data making up the airfoil is how it is stored. Several approaches to parameterization of wing profiles can be found in the literature: Airfoils can be described by point clouds as done in most airfoil libraries [1] or they could be described as mathematical functions as is the case with the NACA 4 digit libraries [2][3] and as the Joukowsky airfoils [4]. A more modern representation method is the class function/shape function transformation CST method [5]. The wing profile representation method used for this paper is the Bézier interpolation developed at Linköping University, described in [6] . The proposed parameterization allows for a very compact wing profile data format, where the position of the control points each is stored as a single digit number in a base 64 space. The entire profile can then be defined as a 13 digit number, which in the same way as the NACA 4 digits profiles, have the name is the airfoil. This paper elaborates on the validation work for the Bézier interpolation. A large number of known wing profiles (1122) have been parameterized to test the validity of the interpolation method. The