| The measurement of surface shear stress is one of the most important research projects in the field of aerodynamics.Shear-sensitive liquid crystal technology is a direct method of non-contact global surface shear stress measurement.The shear-sensitive liquid crystal coatings is sensitive to the applied shear stress.The shear-sensitive liquid crystal produces a color spectrum when illuminated by white light.The color of the shear-sensitive liquid crystal is known to vary with the shear stress direction,magnitude and angles of observation when surface shear stress acts.The color information of different circumferential angle is fitted by Gauss curve,the peak of the curve and angle corresponding to the peak of the curve are the magnitude and direction of the shear stress,respectively.Based on the shear-sensitive liquid crystal technology,a experimental apparatus was designed and built to globally display and measure the surface shear stress of the typical high-speed flow field in nozzle flow under different NPR conditions,including flat wall jet,delta wing induced eddy current,the flow around a thin cylinder and wedge flow structure.Comparing with oil flow,PIV and other technologies,potential of shear-sensitive liquid crystal technology was proven in flow visualization and quantitative measurement.The supersonic flow pattern including shock wave is one of the representative flow structure.In this paper,the Mach disk structure produced by the M1.2 nozzle was used as the test flow field to measure the shear stress vector distribution of the shock wave / shock wave interactions and the shock wave reflective structures.The frictional line spectra and directions map were given.The wedge was installed on the upper wall of M2.7 nozzle to generate incident shock waves.The separated and reattached flow field structure under the influence of incident shock waves was display.The measured results were in good agreement with the Schlieren images. |
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