Assessment of two fluidic actuators for active flow control on a one-sided diffuser

Abstract

The manipulated flow along a one-sided diffuser is investigated experimentally by means of particle image velocimetry and wall pressure measurements. Two fluidic actuators are considered: a fluidic diverter emitting two alternately pulsed jets and a fluidic oscillator generating one spatially oscillating jet. Active separation control is performed with these devices to suppress the pressure-induced separation bubble present in the uncontrolled flow field. The method of proper orthogonal decomposition is employed to identify inherent physical mechanisms subject to varied jet emission angles as well as actuation intensities and construct a reduced order model by utilizing modal coefficients to obtain phase information regarding the periodic actuation process. As a main result, we show that longitudinal vortex structures determining the separation control capability, are more distinct for the fluidic oscillator. Furthermore, the flow fields manipulated by both actuators at a low momentum input are dominated by a spatial mode resembling the base flow. However, this feature is suppressed by the fluidic diverter at greater velocity ratios, whereas the variation of actuation intensity does not yield significant alterations to the spatial modes observed for the fluidic oscillator.