Measurement of Boundary Layer Transition on Oscillating Airfoil using cntTSP in Low-Speed Wind Tunnel

Abstract

cntTSP is a flow visualization technique combining temperature-sensitive paint (TSP) and carbon nanotube (CNT). TSP is a sprayable temperature sensor, and CNT is used as a thin inner electric heater for TSP. The cntTSP technique allows visualizing a dynamic boundary layer transition on a moving airfoil in the low-speed condition. In this study, cntTSP was used to visualize a movement of the dynamic boundary layer transition on a pitch-oscillating airfoil in the low-speed wind tunnel. The transition position was evaluated by using a heat transfer coefficient. At a high reduced frequency, the detected transition positions were different between pitching-up and pitching-down procedure, and hysteresis was observed. Moreover, we observed not only the unsteadiness of the aerodynamic phenomenon due to the pitch-oscillation but also the thermal delay due to the response time of the cntTSP.