| Color change characteristics of two shear-sensitive liquid crystal mixtures （BCN/192, BN/R50C） and their application in surface shear stress measurements |
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| 作者姓名： | ZHAO JiSong SCHOLZ Peter GU LiangXian |
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| 作者单位： | [1]School of Astronautics, Northwestern Polytechnical University, Xi＇an 710072, China [2]Institute of Fluid Mechanics, TU Braunschweig, Braunschweig 38106, Germany |
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| 基金项目： | supported by the Doctorate Creation Foundation of Northwestern Polytechnical University （CX200902） |
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| 摘 要： | A previously determined surface shear stress measurement technique using shear-sensitive liquid crystal (SSLC) coating is extended for use in wind tunnel-like conditions. Simple and common everyday equipment is used in the measurement; in particular a tungsten halogen light bulb provides illumination. The color change characteristics of two SSLC mixtures, BCN192 and BN/ R50C, are investigated. BCN/192 is found sensitive to both magnitude and direction of the shear stress at different shear stress levels with little noise, and is suitable for surface shear stress distribution measurements. The spatial shear stress vector distribution beneath a tangential jet is obtained using BCN/192, although the magnitude is not fully calibrated. BN/R50C is found to be sensitive to shear stress magnitude, but only slightly sensitive to shear stress direction at both low and high levels. Moreover, jumps in the reflected hue are found when the viewing orientation is perpendicular to the shear stress direction. These characteristics render the use of BN/R50C for surface shear stress measurement difficult.
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| 关 键 词： | shear-sensitive liquid crystals surface shear stress measurement tangential jet flow |
| 收稿时间： | 24 September 2009 |
Color change characteristics of two shear-sensitive liquid crystal mixtures (BCN/192, BN/R50C) and their application in surface shear stress measurements |
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| ZHAO JiSong,SCHOLZ Peter,GU LiangXian.Color change characteristics of two shear-sensitive liquid crystal mixtures (BCN/192, BN/R50C) and their application in surface shear stress measurements[J].Chinese Science Bulletin,2011,56(27):2897-2905. |
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| Authors: | JiSong Zhao Peter Scholz LiangXian Gu |
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| Institution: | (1) Department of Mechanical Engineering, Faculty of Engineering, Gazi University, 06570 Maltepe, Ankara, Turkey; |
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| Abstract: | A previously determined surface shear stress measurement technique using shear-sensitive liquid crystal (SSLC) coating is
extended for use in wind tunnel-like conditions. Simple and common everyday equipment is used in the measurement; in particular
a tungsten halogen light bulb provides illumination. The color change characteristics of two SSLC mixtures, BCN192 and BN/R50C,
are investigated. BCN/192 is found sensitive to both magnitude and direction of the shear stress at different shear stress
levels with little noise, and is suitable for surface shear stress distribution measurements. The spatial shear stress vector
distribution beneath a tangential jet is obtained using BCN/192, although the magnitude is not fully calibrated. BN/R50C is
found to be sensitive to shear stress magnitude, but only slightly sensitive to shear stress direction at both low and high
levels. Moreover, jumps in the reflected hue are found when the viewing orientation is perpendicular to the shear stress direction.
These characteristics render the use of BN/R50C for surface shear stress measurement difficult. |
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| Keywords: | shear-sensitive liquid crystals surface shear stress measurement tangential jet flow |
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