Dielectric barrier discharge (DBD) plasma actuators can generate a wall jet
without moving parts through interaction between ionized and neutral molecules
in an electric field. The coupling between electro-hydrodynamic, turbulence,
and viscous effects in the flow boundary layer remains unclear and deserves
careful investigation. We present an experimental investigation of momentum
injection by DBD actuators in a U_external = 5 m/s and U_external = 11 m/s
co-flow and counter-flow configuration over a range of VAC = 12 kV - 19.5 kV
peak-to-peak at a frequency of 2 kHz. In the co-flow configuration, the DBD
actuator adds momentum to the boundary layer, similar to an electrohydrodynamic
(EHD) jet in quiescent conditions. In the counter-flow configuration, flow
separation is observed at free stream velocity U_external = 5 m/s. The momentum
displacement in the counter-flow configuration is ~ 6x greater than EHD jet
momentum in a quiescent environment. Both co-flow and counter-flow momentum
injections show diminishing effects with increased external flow speed. This
work highlights that the resulting flow pattern is not a simple superposition
of the EHD jet and the free stream but is determined by a balance between the
inertial, viscous and Coulombic forces of the EHD and the external flow. The
velocity profiles and momentum characteristics can be used to validate
numerical models and inform the design of DBD actuators for active flow
control.Comment: 14 Pages, 13 figure