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Unformatted text preview: 02MSEC-15 An Angle of Attack Correction Scheme for the Design of Low Aspect Ratio Wings with Endplates Michael Soso and Michael S. Selig University of Illinois at Urbana-Champaign Copyright © 2002 Society of Automotive Engineers, Inc. ABSTRACT Low aspect ratio wings are used extensively on open- wheeled race cars to generate aerodynamic downforce. Consequently, a great deal of effort is invested in obtaining wing profiles that provide high values of lift coefficient. If the wings are designed using 2-D methods, then it is necessary to take into account the change in operating angle of a typical airfoil section that occurs when it operates in the downwash generated by the wing. Accounting for this change during the design phase will ensure that the airfoil sections are optimized for their intended operating conditions. The addition of endplates to the wing serves to counteract the magnitude of the change in operating angle by effectively producing an increase in wing aspect ratio. During the design process at UIUC, an empirical method was used to provide an estimate of the effective aspect ratio of the wing and endplate combination. However, owing to concerns about the dependence of the formula on the chord of the endplate beyond the chord of the wing, it was decided to attempt to develop a new effective aspect ratio relation. Using CFD, a study was carried out to investigate the aerodynamic changes that occurred when a low aspect ratio wing was used in conjunction with endplates of varying height and varying chord. The angle of attack of the wing was also changed in the study. The aerodynamic changes were then used to deduce changes in the effective aspect ratio. The resulting data showed that the effective aspect ratio was highly dependent on an increase in the height of the endplate and slightly dependent on changes in the wing angle of attack. There was no significant dependence on the chord of the endplate beyond the chord of the wing. These results were then used to develop a formula linking the aspect ratio of the wing to the effective aspect ratio of the wing/endplate combination INTRODUCTION BACKGROUND - The field of aerodynamics is one of the major areas of research and development in modern motorsports, a consequence of the fact that many different avenues that can be exploited in order to effect continuous improvement to the race cars [1, 2]. Possibly the most intensely researched area centers around the generation of maximum downforce on the cars. Downforce is needed on race cars because it enhances the performance envelope of the vehicle by providing an increase in its lateral acceleration and braking capabilities [3–5]. Ultimately, the performance gain leads to a reduction in lap times as the vehicle becomes more competitive. The wings on a race car generate the majority of the available downforce, therefore a great deal of attention is given to the proper design and analysis of these components....
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This note was uploaded on 10/20/2010 for the course AERONAUTIC A.E. taught by Professor Allwyn during the Spring '10 term at Anna University Chennai - Regional Office, Coimbatore.
- Spring '10