RESEARCH ARTICLE Evaluation of thrust measurement techniques for dielectric barrier discharge actuators Ryan Durscher • Subrata Roy Received: 12 August 2011 / Revised: 25 June 2012 / Accepted: 26 June 2012 / Published online: 18 July 2012 Ó Springer-Verlag 2012 Abstract Despite its popularity in the recent literature, plasma actuators lack a consistent study to identify limi- tations, and remedy thereof, of various thrust measurement techniques. This paper focuses on comparing two different experimental techniques commonly used to measure the global, plasma-induced thrust. A force balance is used to make a direct measurement of the thrust produced, which is then compared with a control volume analysis on data obtained through particle image velocimetry. The local velocity measured by particle image velocimetry is also validated with a fine-tip pressure probe. For the direct thrust measurements, the effect of varying the actuator plate length upon which the induced flow acts is investi- gated. The results from these tests show that the length of the actuator plate is most influential at higher voltages with the measured thrust increasing as much as 20 % for a six times reduction in the length of the plate. For the indirect thrust measurement, the influence of the control volume size is analyzed. When the two methods are compared against each other, good agreement is found when the control volume size has a sufficient downstream extent. Also, the discharge length is optically measured using visible light emission. A linear correlation is found between the discharge length and the thrust measurements for the actuator configurations studied. Finally, the energy conversion efficiency curve for a representative actuator is also presented. 1 Introduction The dielectric barrier discharge (DBD) plasma actuator, in general, consists of an asymmetric electrode arrangement (one exposed and one encapsulated) separated by a dielectric medium. The application of an alternating, high- voltage signal results in a surface-mode discharge along the dielectric. At (or near) atmospheric pressures, the discharge is comprised of micro-discharges which form discrete channels between the electrode and dielectric surface (Gibalov and Pietsch 2000; Kogelschatz 2003; Xu 2001). The expansion of the discharge along the dielectric surface results in a charge deposition, which in turn reduces the local electric field and extinguishes the micro-discharge. Collectively, the discharge is completely extinguished twice per period as evident by the light emission and dis- charge current (Enloe et al. 2004). As the ionized particles within the micro-discharges propagate along the dielectric surface, momentum is transferred to the surrounding neu- tral particles through a poorly understood collisional mechanism. Macroscopically, however, the net separated space charge within the plasma interacts with the electric field resulting in an electro-hydrodynamic body force act- ing on the working gas resulting in an acceleration of the fluid. By virtue of Newton’s third law, an equal and opposite force is imparted to the actuator. Experiments have shown this momentum exchange to be cyclic with the magnitude of the force varying depending on the polarity of the exposed electrode (Debien et al. 2012, Enloe et al. 2008b; Enloe et al. 2009; Font et al. 2011). The plasma actuator has been used as a flow control mechanism in various aerodynamic applications such as turbines blades (Ramakumar and Jacob 2005; Rizzetta and Visbal 2008), landing gears (Thomas et al. 2005), airfoils (Little et al. 2010; Post and Corke 2004), turbulent jets R. Durscher  S. Roy (&) Applied Physics Research Group, Mechanical and Aerospace Engineering Department, University of Florida, Gainesville, FL 32611-6300, USA e-mail: roy@ufl.edu 123 Exp Fluids (2012) 53:1165–1176 DOI 10.1007/s00348-012-1349-6