Computational fluid dynamics for aerodynamic design - Its current and future impact

This paper discusses the role that computational fluid dynamics plays in the design of aircraft. An overview of the design process is provided, covering some of the typical decisions that a design team addresses within a multi-disciplinary environment. On a very regular basis trade-offs between disciplines have to be made where a set of conflicting requirements exist. Within an aircraft development project, we focus on the aerodynamic design problem and review how this process has been advanced, first with the improving capabilities of traditional computational fluid dynamics analyses, and then with aerodynamic optimizations based on these increasingly accurate methods. The optimization method of the present work is based on the use of the adjoint of the flow equations to compute the gradient of the cost function. Then, we use this gradient to navigate the design space in an efficient manner to find a local minimum. The computational costs of the present method are compared with that of other approaches to aerodynamic optimization. A brief discussion regarding the formulation of a continuous adjoint, as opposed to a discrete one, is also included. Two case studies are provided which highlight the benefits of utilizing automatic aerodynamic shape optimization. The first case chronicles the application of such software during a complete aircraft design effort, while the second case shows to what extent the aerodynamic design cycle can be compressed. In both efforts, the optimizations were performed in design spaces with dimensions greater than 4, 000. Furthermore, they were conducted on very affordable computer equipment and turned around within a few hours of wall-clock time. ∗AIAA Fellow, T. V. Jones Prof. of Engineering †AIAA Associate Fellow, Boeing Technical Fellow Copyright c ©2001 by Jameson & Vassberg. Published by the AIAA with permission. The paper finishes with some visions for the future. Extrapolating the trends of computer weight and cost, it is interesting to speculate on how the aircraft design environment may evolve in the years to come.