Drag reduction control for blunt body in cross flow using flap actuators

Active flow control, which can adapt to variable cross flow direction, is an effective technique to achieve drag reduction. The present study has investigated the effect of flap actuators to the blunt body and established a drag reduction control system for variation of cross flow direction. Numerical simulations were performed in order to obtain the optimal flap positions for drag reduction. A three force components transducer was introduced to measure drag force in order to investigate optimal flap angle to the flow direction. And flow structure around the body was examined using PIV (Particle Image Velocimetry). In this drag reduction system, flap actuators were controlled to the optical angle by detection of flow direction by investigation of non-separating flow, using pressure transducers as sensors. The flap actuators at the leading edge of the body promoted separated shear layer to approach to the body and lead to drag reduction at the optimal flap angle. Drag reduction rate is up to about 30%. This drag reduction control system adapted to variable cross flow direction raging from 0 to 40 deg. and reacted for drag reduction in 0.1 s.