Applications of a Direct / Iterative Design Method to Complex Transonic

The current study explores the use of an automated direct/iterative design method for the reduction of drag for transport con gurations, including con gurations with engine nacelles. The method requires the user to choose a proper target-pressure distribution and then develops a corresponding airfoil section. The method can be applied to two-dimensional airfoil sections or to three-dimensional wings. The three cases that are presented show successful application of the method for reducing drag from various sources. The rst two cases demonstrate the use of the method to reduce induced drag by designing to an elliptic span-load distribution and to reduce wave drag by decreasing the shock strength for a given lift. In the second case, a body-mounted nacelle is added and the method is successfully used to eliminate increases in wing drag associated with the nacelle addition by designing to an arbitrary pressure distribution that has an elliptic span-load distribution with reduced shock strength. The third case does not show a large drag decrease, but does demonstrate the elimination of nacelle in uence on the original pressure distribution as a result of the redesigning of a wing in combination with a given underwing nacelle to clean-wing, target-pressure distributions. These cases illustrate several possible uses of the method for reducing di erent types of drag. The magnitude of the obtainable drag reduction varies with the constraints of the problem and the con guration to be modi ed.