| When hypersonic aircraft is searching target with imaging guidance,the harsh aerodynamic environment it faced will cause two major problems: the protection of window from dynamic heating and the control of flow to eliminate aero-optical distortion.Cooling with gas film is an active and effective method which both meets the cooling requirements of the imaging window and the light transmission around the window.By studying the flow mechanism and control of the cooling film,it is expected to reduce the interference of various complex flow structures to the optical transmission while satisfying the cooling requirements.Thus,the image quality can be improved and the goal of improving the guidance precision can be achieved finally.In this paper,Nano-tracer Planer Laser Scattering(NPLS)is used as the main experimental method.Combined with fractal dimension,intermittent analysis and other data processing methods based on NPLS results,the structure and spatiotemporal evolution of the supersonic cooling film flow field under different ratio of static pressure were studied.The control effects of the rough band and the vortex generator on the flow field of the supersonic cooling film were also be studied.In the beginning,the equipment and related testing techniques needed for the experimental study of supersonic film in the hypersonic flow field are introduced.The Mach 6 hypersonic low noise wind tunnel,the NPLS technique of hypersonic flow field and the data processing method based on NPLS results,such as fractal dimension and intermittent analysis,were described in detail.Then,based on the NPLS technique,the experimental study on the flow mechanism of supersonic cooling film in Mach 6 hypersonic low noise wind tunnel was carried out.The experimental model and the flow field parameters were introduced.The results of the flow field of backward facing step without jet were analyzed.Based on the static pressure measured in this experiment,the effect of static pressure ratio on the structure and spatiotemporal evolution of supersonic gas film flow field was studied by analyzing the fine structure of flow field.Finally,the experimental study on the control of supersonic cooling gas film in hypersonic flow field is carried out.How the flow field control element was selected and distributed was introduced.Under the pressure matching condition,the experiment aiming to study how the flow field of supersonic cooling film was controlled by different height vortex generators and different mesh roughness was carried out.With the fractal dimension and intermittent analysis,the effects of height and mesh on the control effect were discussed. |
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