Impact onto the boundary layer on the airfoil of a small-sized flying vehicle with the use of a wavy surface. Problems and prospects (review)

A method is proposed to improve the aerodynamic performance of small-sized flying vehicles. The method is based on fundamental gas-dynamic phenomena, such as local separation of the boundary layer accompanied by the formation of the so-called separation bubbles, separation of the turbulent boundary layer, and flow shedding from the leading edge of the airfoil, which alter the entire flow structure around the body. Publications where the relationship of these phenomena is established and those that describe a control method eliminating the adverse consequences of flow separation with the use of a wavy surface of the airfoil are reviewed. The method is simple in implementation and offers many prospects. The area of its applicability are determined, and criteria of optimizing the wavy surface of the airfoil for particular operation conditions are provided. Results of investigations are reported, which show that the use of a wavy surface of wings or blades of flying vehicles can improve their aerodynamic characteristics. Various structural elements of the boundary layer are noted, such as local separation bubbles or a general separation region, and criteria of their emergence are given, which assists in verification of numerical experiments.