Effect of Plasma Actuator Placement on the Airfoil Efficiency at Poststall Angles of Attack

Abstract

One of the new techniques in active flow control is the single-dielectric barrier discharge plasma actuator, which postpones the separation with external momentum injection to the boundary layer flow. In this paper, the effect of the presence of a plasma actuator on the passing flow is investigated both numerically and experimentally at a poststall angle of attack NLF0414 airfoil. These investigations are performed for a 45-cm cord NLF0414 airfoil with an incompressible 25-m/s velocity airflow, which provides a turbulent flow. Both numerical and experimental studies are done under the same conditions for two different cases: 1) no plasma actuator is located on the airfoil and 2) a plasma actuator is located on the top surface of the airfoil. Simulating the flow over the airfoil with the presence of a plasma actuator at 9.6 mm from the leading edge of the airfoil showed that the numerical distribution of the body force induced by the plasma actuator (computed using the model presented by Suzen <etal xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> ) is in an appropriate correlation with the experimental results. It has been also shown that the presence of the plasma actuator on the airfoil could delay the separation and subsequently increase the airfoil's efficiency. Initially, the experimental and numerical results were compared and the written code, for simulation of the body force produced by the plasma actuator was verified. Then, the effect of the plasma actuator's location on the separation's delay at different angles of attack was numerically studied. In this case, the place of the plasma actuator on the airfoil was changed and its effect on postponement of the separation point was investigated. The results show that when the actuator is placed exactly at the leading edge of the airfoil, it has the greatest influence on postponing the separation. In addition, at an angle of attack of 18 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> , it transfers the separation point from 16 to 90 mm. In addition, it results in an increase of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\sim}{100\%}$</tex></formula> in the efficiency (the ratio of lift to drag coefficient) of the airfoil at this angle of attack.