Abstract:
The objective of this paper is to develop a boundary layer transition detect technique based on IR technique for laminar wing glove flight test. The main factors of flight environment affecting the technique were analyzed, including optical path, wing skin surface processing method, and heating etc., and then the technique solutions for these influence factors were proposed. A flight test was designed to validate the IR transition detection method, and a classic civil aircraft was used as the test platform. The flight altitude was from 5 km to 7 km, and the flight Mach number was from 0.5 to 0.65. To analyze the effects of wing heating system and solar radiation on IR map, IR images acquisitions were carried out under conditions that the wing heating system was pulse-on and pulse-off. Furthermore, a shadow on the measurement region was built to utilize the azimuth between the airplane and sun. Several flights were carried out to show the effects of the leading edge pollutants on laminar boundary layer. A transition position determination method based on statistical analysis was proposed to avoid misjudgment of the transition position from turbulent wedges induced by leading edge pollutants. Standard circle roughness elements were used to validate IR measurement results. The test results show that the SNR can be increased significantly by wing skin surface heating. Three sets of wing boundary layer transition position under flight conditions are provided, and the Reynolds number is larger than 13 million. Compared with fixed transition, the error of transition position measured from IR image is less than 0.5% chord length. The transition detection method proposed in this paper is appropriate for the laminar wing glove flight test.