Aerodynamic shape optimization of co-flow jet airfoil using a multi-island genetic algorithm

The co-flow jet is a Zero-Net-Mass-Flux (ZNMF) active flow control strategy and presents great potential to improve the aerodynamic efficiency of future fuel-efficient aircraft. The present work is to integrate the co-flow jet technology into aerodynamic shape optimization to further realize the potential of co-flow-jet technology and improve co-flow jet airfoil performance. The optimization results show that the maximum energy efficiency ratio of lift-augmentation and drag-reduction increased by 203.53% (α=0◦) and 10.25% (α=10◦) at the Power-1 condition (power coefficient of 0.3), respectively. A larger curvature is observed near the leading edge of the optimized aerodynamic shape, which leads to the early onset of flow separation and improves energy transfer efficiency from the jet to the free stream. In addition, the higher mid-span of the optimized airfoil is characterized by accelerating the flow in the middle of the airfoil, increasing the strength of the negative pressure zone, thus improving the stall margin and enhancing the co-flow jet circulation.