Adaptive Control of Shock Waves with a Passively Morphing Layer for Rotating Blades

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Helicopter blades are known to experience complicated unsteady flow conditions during high-speed forward flight. Transonic shock takes place along the advancing side, which decreases the performance of the blades and results in impulsive noise. Adaptive airfoils seem promising for increasing performance at considerably variable flow conditions. In this paper, a blade with a passively morphing layer is presented for transonic shock/boundary layer control at forward flight conditions. The morphing layer embedded in the upper surface of the blade can form an adaptive bump, which in turn can control transonic shock/boundary layer interaction. A fluid-structure-interaction (FSI) enabled simulator is employed to study the performance of the morphing layer at two different forward conditions. The results demonstrate that the adaptive bump formed by the morphing layer could efficiently weaken the strong normal shock over the layer by producing a λ-structural shock. Moreover, the morphing layer retreats to its undeformed state to prevent detrimental effects at weaker shock or shock-free flow. To further increase the performance of the morphing layer, a morphing layer that is inclined with respect to the spanwise direction is used to replace the layer that lies parallel to the spanwise direction. The results indicate that the inclined morphing layer performs better while the shock position takes on a less uniform distribution.