Inﬂuence of circulation on a rounded-trailing-edge airfoil
using plasma actuators
Received: 21 December 2013 / Revised: 11 April 2014 / Accepted: 18 June 2014 / Published online: 28 June 2014
Ó Springer-Verlag Berlin Heidelberg 2014
Abstract An experimental study on inﬂuence of circu-
lation around a symmetric airfoil with a rounded trailing
edge is presented. Flow control is achieved by the use of
dielectric barrier discharge plasma actuators placed at the
trailing edge of the airfoil. Direct lift and drag measure-
ments are taken using an external load balance at free-
stream velocities of 10, 15 and 20 m/s corresponding to
chord Reynolds number of 140,000, 210,000, 280,000.
Additionally, time-resolved particle image velocimetry is
used in order to elucidate the topology and dynamical
response of the wake ﬂow under the inﬂuence of actuation.
Results indicate an increase in lift coefﬁcient of approxi-
mately 0.1 for the lowest tested Reynolds number using the
plasma actuator. Flowﬁeld measurements indicate the
successful manipulation of the Kutta condition enabled by
the plasma actuator. The actuator is enhancing the mixing
of the wake near the trailing edge while reducing the
dominant shedding frequency. Proper orthogonal decom-
position analysis reveals further details regarding the
dynamics of the wake ﬂow in presence of actuation, sug-
gesting the sensitivity of the control concept to the posi-
tioning of the actuator as well as the angle of attack.
Active ﬂow control for dynamic lift manipulation has been
in the focus of the wind energy industry in recent years
(Barlas and Kuik 2010). The continuously increasing size
of wind turbines creates the need for efﬁciently reducing
fatigue load on the blades induced by unsteady wind or
gusts. Suppression of these unsteady loads by passive or
active means has the potential of mitigating fatigue and
allow for thinner and cheaper blade walls as well as lower
Active load control involves the control of the local
airﬂow around a lift generating body in order to achieve
variations in the components of aerodynamic forces, typi-
cally with emphasis on lift. Ideally, the control and the
produced change in lift need to be applied within short
response times corresponding to unsteady atmospheric
conditions such as wind gusts or the rotational frequency of
the blade. Several studies have been performed on concepts
of active load control such as trailing edge ﬂaps (Buhl et al.
2005), microtabs (Yen Nakafuji et al. 2001), vortex gen-
erators (Lin 2002), blowing and suction (Seifert et al. 2004)
and classical circulation control (Englar 2000).
A recent technology for ﬂow control is plasma actuators.
These have low power consumption, lack of moving parts
and extremely short response times since they operate in
electrical rather than mechanical timescales. There are
several implementations of the actuators, the most popular
being the dielectric barrier discharge (DBD) kind (Fig. 1).
These are based on the ionisation of air via an AC high-
voltage (HV) signal. Two electrodes are usually employed,
one being grounded and the other carrying the HV signal.
The electrodes are separated by a dielectric layer which
prohibits arc forming and allows for the ionised gas to
accumulate on the surface. The mechanism of the
M. Kotsonis (&) Á L. Veldhuis
Faculty of Aerospace Engineering, Delft University of
Technology, 2629 HS Delft, The Netherlands
Vostermans Ventilation, 5902 RA Venlo, The Netherlands
Exp Fluids (2014) 55:1772