Numerical Simulations of NS-DBD Plasma Actuators For Flow Control

Numerical Simulations of NS-DBD Plasma Actuators For Flow Control

Popov, I. (TU Delft Aerodynamics)

Scarano, F. (promotor)
Hulshoff, S.J. (copromotor)

Delft University of Technology

2016-03-22

Nanosecond dielectric barrier discharge (NS-DBD) plasma actuators is relativelynew means of flow control. It has several advantages compared to more conventionalmeans of flow control, such as small size, low weight, fast response timeand controllability. It has been demonstrated to be able to promote transition ofboundary layers and to postpone flow separation on aerodynamic surfaces. Thismakes the NS-DBD actuator a promising technology for many applications inaerospace and wind energy industries.This thesis presents a study of NS-DBD actuator effects by numerical simulations.For the purposes of simulations of fluid-dynamic effects of the actuation,complex plasma dynamic processes are modeled by their thermal effects. Thisis possible due to a large separation of scales between plasmadynamic, thermodynamicand fluid dynamic phenomena. The resulting model is embedded intothe compressible computational fluid dynamics (CFD) simulation using Navier-Stokes equations. This model is then used in numerical simulations in two modelflows: a laminar boundary and a free shear layer. These model flows are relevantfor promotion of laminar to turbulent boundary layer transition and laminarleading edge separation elimination.For the laminar boundary case, the effect of a burst of discharges on a flatplate boundary layer is studied. The shape, wavelength and propagation speed ofthe disturbance introduced into the boundary layer by actuation are compared toexperimental results and found to be in agreement. This indicates that the thermalmodel is adequate at predicting phenomenological effects of the actuation in thiscase. POD analysis of the CFD flow fields is employed to identify the dominatingmodes of the disturbance. The dominating mode is found to be the same asthe least stable mode predicted by linear stability theory. A compression wave,however, is not found to play an important role, and the burst of pulses is foundto produce the same effects as the long pulse with the same total energy.For the free shear layer case, the model of the actuator is placed on a centerlinein the beginning of a free shear layer. As a result of constant frequency actuation,early formation of vortices and shear layer breakdown are observed. Each actuation event produces a convective disturbance in the flow field. Dynamics of thedisturbances are analyzed and growth rates are found to be in agreement with thepredictions of linear stability theory. A parametric study is carried out to studyscalability of the actuator effects to change of actuation frequency and energy perpulse. A saturation effect with the increase of actuation frequency is observed.For both studied cases, the effect of NS-DBD actuation is excitation of naturalinstability modes, which then evolve according to the stability properties of theflow.

flow control
plasma
transition
flow separation
plasma actuators
DBD
NS-DBD

https://doi.org/10.4233/uuid:f2fa6bd6-4419-494c-ab14-f0c1ec020270

ISBN 978-94-6186-617-2

Institutional Repository

doctoral thesis

© 2016 I. Popov