Investigating Fluidic Oscillators Embedded in a Slotted-Natural Laminar Flow Airfoil for High-Lift Applications

Abstract

Fluidic oscillators were embedded into a slotted natural laminar flow airfoil to increase the circulation around the airfoil system and improve its performance under high-lift configurations. The fluidic oscillator internal geometry was designed to produce a frequency to match the natural shear-layer instabilities and target F^+=0.1. The S207 SNLF airfoil was analyzed in a wind tunnel with freestream conditions of M=0.15 and Re=1.2×10^6. Morphed leading edge designs and aft element deflections were coupled with embedded fluidic oscillators to provide a systematic approach to high-lift devices on the SNLF airfoil. While active flow control had a minimal effect on the lift of the airfoil at all mass flow settings, there was a significant and steady reduction in drag as active flow control mass flow increased. The drag reduction resulted in L/D increases up to 40% when comparing active flow control against no flow control. Additionally, stereo-PIV showed how the inclusion of active flow control led to a reduction and delay in separation across the aft element.