On design optimisation based control methods for distributed suction for boundary layer transition control

Turbulent flow has a significantly higher drag than the corresponding laminar flow for the same flow conditions. The presence of turbulent flow over a large part of an aircraft therefore incurs a significant penalty of increased fuel consumption due to the extra thrust required. One possible way of decreasing the drag is to apply surface suction to delay the transition from laminar to turbulent flow. However, in order for the gain from the reduction in drag to outweigh the extra costs associated with the suction system, the suction must be distributed in an optimum, or near optimum, manner. This paper investigates methods for the design of multi-panel suction systems using optimisation methods based on direct search techniques. It is shown that for the problems considered, good solutions can be found efficiently.