CFD now stands alongside the wind tunnel in terms of importance to aerodynamic design. Its usage by engineering designers involves many thousands of runs per year, and the rate is increasing. For the simpler aerodynamic flows where viscous effects are modest, CFD has become the dominant tool for aerodynamic design. The primary role of the wind tunnel for such flows is for validation of a design and for determination of aerodynamic characteristics over the broad flight envelope. For more complex flows that are dominated by strong viscous effects, CFD is beginning to make a contribution.
It is thought by many that the principle challenge for the future is to develop better computers and algorithms in order to better address the computation of complex flows over complex airplane geometries. But recent experiences involving the application of CFD to the design of the new Boeing 777 airplane has taught us that the challenge for the future is really much broader. This recent experience has brought into focus a clearer understanding of where the leverage of CFD really is, and what codes must be able to do in order to contribute in truly significant ways to the design of superior airplanes. This paper discusses the characteristics of the codes that are found to play a truly central and effective role in airplane design, and describes the challenges that must be met and overcome.