Fiber optic pressure measurement on a complex outer winglet model with active flow control actuators

Abstract

The next generation of aircraft requires novel approaches on lift increase and drag reduction technologies as active flow control to counter local flow separations. Testing and monitoring its effectiveness in flight require precise pressure evaluation as a possible control input. Pressure-based measurements of local flow separation are challenging utilizing conventional electrical pressure sensors. These sensors might show degradation of their long-term performance in harsh environments, e. g., in real aircraft applications, due to their low overload protection, susceptibility to electromagnetic influences, and corrosion. Fiber optic measurements overcome those challenges and promise to be a robust sensing solution. We investigate the potential application of a novel fiber optic measurement system that monitors the active flow control system's effectiveness. Furthermore, the results are compared to conventional static pressure measurements. Due to the high-frequency capabilities of the fiber optic sensors, the dynamic behavior of the boundary layer separation and vortex generation was captured in the frequency domain. An industry-relevant outer wing was equipped with 25 fiber optic pressure sensors positioned at one wingspan section for this experiment. The experiments were conducted at a Reynolds number Re=1.1⋅106and a Mach number Ma=0.12. Wind tunnel testing results show that fiber optic pressure sensors can measure aerodynamic characteristics and, furthermore, even allow a detailed look at the dynamic behavior.