An overview of blowing and suction perforations for boundary layer control on airfoils

Boundary-layer separation remains one of the primary challenges in aerodynamic design, significantly influencing lift, drag, and stall behaviour in airfoils and related systems. Boundary Layer Control (BLC) techniques based on blowing and suction through perforated surfaces have gained increasing attention due to their ability to delay separation and enhance aerodynamic efficiency. However, existing research remains fragmented across active and passive control strategies, and a comprehensive synthesis of their performance characteristics is still limited. This review compiles and analyses findings from peer-reviewed studies on BLC, focusing on the aerodynamic effects of blowing and suction through perforated airfoil surfaces. The collected literature is classified into active and passive control strategies and includes steady and synthetic jet actuation, as well as porous configurations. Key design parameters such as jet number, location, orientation, velocity ratio, and orifice geometry are examined to evaluate their influence on flow separation suppression, wake modulation, dynamic stall mitigation, and lift-to-drag enhancement. The review compares experimental and computational results, highlighting consistent trends in jet configuration performance, Reynolds number sensitivity, and unsteady flow response. Active control methods, especially steady and synthetic jets, provide highly tunable and efficient means of improving aerodynamic performance, while passive approaches, such as perforated or porous surfaces, are advantageous for low-energy or geometrically constrained applications, although they exhibit lower control authority. The reviewed studies indicate that blowing and suction through perforated surfaces can significantly improve boundary-layer behaviour under specific flow conditions. Active techniques, particularly steady and synthetic jets, demonstrate high control authority and adaptability, while passive methods offer energy-efficient alternatives with more limited effectiveness. However, performance remains strongly dependent on design parameters such as jet configuration, location, and momentum input. Therefore, further research is required to optimise these systems under varying aerodynamic conditions.