Drag reduction for three dimensional wing at transonic speed

At transonic speeds, wave drag is the bottleneck for wings at low wing sweep angles. The ability to alleviate the wave drag is a crucial requirement for future low drag large transport aircraft, in particular, for natural laminar flow transonic wings.

Shock control bumps are effective devices for improving the aerodynamic efficiency for transonic aircraft. From the previous research, the peak location and bump height are the most sensitive parameters; therefore the deployment position and size of the shock control bump are key factors. The position and size of shock control bumps are based on the designers' experience and their view of shock location.

In this test case, a fixed wing, the ONERA M6 wing, at transonic condition is taken as the baseline. The transonic flow exhibits a λ–shock wave on the upper surface of the wing, which provides an interesting case for shock control study.

An array of shock control bumps are deployed in this area and optimized using a gradient based approach. In addition to the sensitivity in the shock regions a non-shock region is identified using the sensitivity map on the wing. This region is not identified in other plots such as pressure or skin friction and could be overlooked by a designer without the sensitivity map. The results show that the mesh adjoint approach successfully identifies the drag sensitive areas on the upper wing and assists in the deployment of the bump arrays quickly, and the class/shape function transformation (CST) bump provides a highly flexible design space, with a large number of design variables, to achieve an optimal solution.