Infrared thermography experiments of hypersonic boundary-layer transition on a 7° half-angle sharp cone

In order to promote the in-depth research on the hypersonic boundary layer transition and provide basic wind tunnel experimental data for the study of the boundary layer transition mechanism, the physical model validation, and the transition database construction, infrared thermography experiments of boundary layer transition are carried out in the Φ1 m hypersonic wind tunnel at CARDC. The effects of different unit Reynolds numbers, angles of attack and Mach numbers on the transition positions are studied on a 7° half-angle sharp cone. Test unit Reynolds numbers range from 0.49×10⁷/m to 2.45×10⁷/m. Test angles of attack range from -10° to 10°. Test Mach numbers range from 5 to 7. The head radius of the test model is 0.05mm. The quantitative infrared thermography technique is employed to obtain the temperature distribution photos of the model surface. By this way, the accurate transition positions and the effects of transition factors are obtained. Test results of the global temperature distribution show that an earlier transition occurs with the increase of Mach number. This is due to the larger Reynolds number and stronger flow field noise brought by the higher Mach number. As the unit Reynolds number increases, the transition position of the boundary layer moves forward and the transition Reynolds number remains constant about 3.0×10⁶. When the angle of attack is small, a delayed transition occurs on the windward side and an earlier transition occurs on the leeward side with the increasing angle of attack. When the angle of attack is 10°, an earlier transition occurs at the center line of the windward side and reversed transition with angle of attack takes place, accompanied with a low heat flow strip induced by the flow separation on the leeward side.