Steady-State Closed-Loop Control of Bypass Boundary Layer Transition Using Plasma Actuators

Abstract

The overarching objective motivating this work is a physical demonstration of modelbased, closed-loop control of bypass transition using plasma actuators. The present work is concerned with the closed-loop control of bypass transition using plasma actuators. This manuscripts extends the work by Hanson et al., 1, 2 who demonstrated that a spanwise array of plasma actuators can produce significant attenuation of the transient growth disturbances introduced by roughness elements. In the present work, the control loop is closed based on feedback from wall-shear stress measurements. The control signal is based on empirical modelling of the input/output flow response for several flow conditions. The latter is obtained for both the main disturbance, generated by a roughness-element array, as well as the control disturbance, forced using a spanwise plasma actuator array. The output is characterized using wall-shear-stress measurements downstream of the actuation location. The controller is designed to minimize the residual disturbance energy in the output measurements at the target instability spanwise wavenumber. The control model developed in this work was applied to three steady disturbance cases, including one that is outside of the parameter range for which the input/output model was developed. The closed-loop control model is shown to effectively attenuate the boundary layer disturbance by Ω 1,end > 95% in each case, with the initial control iteration accounting for Ω1,1 > 89%.

Reactive control of isolated unsteady streaks in a laminar boundary layer

“…Plasma actuator SDBD plasma actuators (hereafter simply referred to as plasma actuators), provide a uniquely deployable, robust and adjustable amplitude flow forcing that is appropriate for the target control experiments (Hanson et al 2010(Hanson et al , 2012(Hanson et al , 2014Osmokrovic et al 2015). A comprehensive description of this type of a plasma actuator arrangement may be found in Corke, Post & Orlov (2009) or Benard & Moreau (2014).…”

Experiments for control of boundary layer transition by plasma actuators

“…The plasma excitation's correction effect on the mean flow can be used to suppress the growth of the local 3D cross-flow component in the boundary layer of the swept-back wing model, thereby delaying the transition [7]. Based on the feedback from the wall shear stress test, adjusting the plasma actuator layout to generate the flow vortex structure suppresses the flow stripes in the bypass transition at the IOP Publishing doi:10.1088/1742-6596/2730/1/012055 2 incoming flow velocity of 5 m/s, thus delaying the transition [8][9]. To delay the transverse turning of a conical boundary layer at an incoming flow of 3.5 Ma [10], a plasma actuator is used to generate pairs of counter-rotating vortices that suppress high-harmonic energies and thus delay the transition in a supersonic boundary layer.…”

Damping of the longitudinal streak in the boundary layer by ‘plasma panel’ actuator

“…Among the other strategies, direct damping of the cross-flow vortices in the boundary layer was theoretically studied in [6]. Plasma actuators, designed as plasma vortex generators (VG), were also used to damp the streaks in the problem of algebraic instability control [12,13].…”