High Frequency Boundary Layer Actuation by Fluidic Oscillators at High Speed Test Conditions

Abstract

Detailed investigations of high frequency pulsed blowing and the interaction with the boundary layer at high speed test conditions were performed on a flat plate with pressure gradient. This experimental testbed features the imposed suction side flow of an aerodynamically highly loaded low pressure turbine profile. For actuation, a newly developed coupled fluidic oscillator with an independent mass flow and frequency characteristic was tested successfully. Several oscillator operating points were investigated at one turbine profile equivalent operating point with Reynolds number of 70,000, theoretical outflow Mach number of 0.6, and an inflow free stream turbulence level of 4%. The examined frequency range was between 6.5 and 7.5 kHz and the actuation mass flow rates were varied between 0.68% and 1.32% of the overall passage mass flow. As a result, the flow separation and transition can be controlled and the suction side profile losses even halved. Differences in the interaction with the boundary layer of the different oscillator operating points are also presented and discussed.