Active Drag Reduction

The Active Flow Control Over the Trailing Edge of a Symmetrical Airfoil Using Plasma Actuators

Flow control in a general sense includes performing favorable changes in the fluid flow for specific goals, such as reducing drag force, increasing lift force or the ratio of lift to drag, as well as preventing or postponement of flow separation. There are few studies conducted on the airfoil performance increment by active control of the flow at the trailing edge. Gurney flap is a lift increasing device for which experimental studies show a considerable increment in the airfoil lift force. In the present work, the feasibility of using plasma actuators for producing artificial micro-tab and Gurney flaps has been studied experimentally. A plasma actuator consists of two electrodes and a dielectric layer. The high potential difference between the two electrodes causes the ionization of the nearby air. This creates a flow jet in the vicinity of the surface flowing downstream. The most important advantages of plasma actuators compared to other flow control methods include; simplicity, performing at different frequencies, fast response times for unstable methods, low weight, and the ability to install on different geometries. Choosing different test scenarios, in terms of configuration, actuator position, and the number of actuators, we have studied aerodynamic performance improvement of an airfoil. The tests are conducted on a NACA 0015 airfoil at Reynolds numbers of about $10^5$ at different angles of attack of 0 to 15 degrees. The static pressure on the airfoil surface is measured to evaluate the aerodynamic performance. Furthermore, flow visualization has been conducted utilizing a smoke generator and a powerful light source in the form of a laser. This helps with a better understanding of the flow evolution and patterns at the trailing edge of the airfoil.