Flow Control Actuators
Localized Energy Deposition
The potential of localized pulsed energy deposition (i.e. thermal perturbations) as a mechanism for high amplitude, high bandwidth actuation has been demonstrated, but the fundamental physics of how this influences the flow field remain poorly understood. The TFCL investigates the physics and scaling of localized energy deposition from pulsed lasers and pulse plasmas in various canonical turbulent flows.
Figure: A long time exposure of a ns-DBD discharge operated in burst mode at 9 kHz and with an amplitude of 1.2 mJ/cm/pulse at 30% duty cycle. The plasma is constricted along discrete filaments which develop when the peak discharge voltage is high.
Figure: A typical voltage (black) and current (red) trace of an ns-DBD plasma actuator. As the applied voltage increases, the air is ionized and charge flows from the exposed electrode to the dielectric. The accumulation of charge on the dielectric forms a virtual electrode. A second current extremum is created as charge moves back from the virtual electrode to the exposed electrode. Both discharges add thermal energy to the flow.
Fluidic oscillators (also called sweeping jet actuators) are effective tools that can delay boundary layer separation on aerodynamic surfaces. The back and forth sweeping motion of these actuators does not require any moving parts and generates streamwise vortices while adding momentum to the boundary layer. Despite widespread success, the exact mechanism by which they influence the nominally separated flow is still unknown. The TFCL investigates the physics and scaling of these devices in various canonical separated flows.
Figure: Flow visualtization with china clay for Fluidic Oscillator type actuators at 1.5 inch spacing. Tested in a benchtop setting with a massflow of 852 slm supplied to 23 actuators.
Christopher Otto, Philipp Tewes, Jesse C. Little, and Rene Woszidlo. "Comparison of Fluidic Oscillators and Steady Jets for Separation Control on a Wall-Mounted Hump", 2018 AIAA Aerospace Sciences Meeting, AIAA SciTech Forum, (AIAA 2018-1281). https://doi.org/10.2514/6.2018-1281.