OPEN LOOP CONTROL OF A TURBULENT BACKWARD FACING STEP BY DBD PLASMA ACTUATORS

Abstract

A non-thermal surface plasma discharge (dielectric barrier discharge) is installed at the step corner of a backwardfacing step (U0=15 m/s, Reh=30000, Reθ=1650). Wall pressure sensors are used to estimate the reattaching location downstream of the step and also to measure the global wall pressure fluctuation coefficients. A parametric study is performed where the voltage amplitude, the burst frequency and the duty-cycle of the input high voltage are investigated separately regarding their performance. PIV is used to analyse the impact on the dynamic of the flow. The minimum reattaching position is achieved by forcing the flow at the shear layer mode through 2D periodic perturbations in the initial region at Sth=0.25 (Stθ=0.013), where a large spreading rate is obtained by increasing the periodicity of the vortex street and by enhancing the vortex pairing process. A recirculation reduction by 22% is observed. Pressure fluctuations are maximized for an actuation at half the shear layer mode (Sth=0.125 or Stθ=0.006). In this case, the vortex pairing goes along with sequences of single vortex growing by fluid entrainment during their convection.