采用液晶涂层测量介质流与壁面间剪切应力的定量模型与试验研究

张松鹏; 张向军; 田煜; 孟永钢

清华大学,摩擦学国家重点实验室,北京100084

A quantitative model and experimental investigations of wall shear stress between solid and gaseous fluid using liquid crystal coating

摘要: 流场中介质流与壁面间剪切应力的定量测量，在运动物体例如航天器等的表面流场观测与表面减阻等领域有重要意义．本文采用向列相液晶涂层技术针对介质流与固体壁面间的剪切应力展开定量测量．首先利用液晶弹性变形理论建立了向列相分子在剪切应力场作用下旋光性光强信号与剪切应力大小的定量模型；进而，在固体表面制备了5CB与7CB向列相液晶涂层，采用搭建的实验装置对不同剪切应力场下的测试涂层的光强进行了测试与理论模型的计算模拟，测试结果与定量模型相当吻合；进一步探讨了液晶涂层测试技术的极限剪切应力、灵敏范围以及涂层膜厚、分子弹性等关键影响因素．

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Abstract: Measurement of wall shear stress (WSS) has important significance in many fields, such as spacecraft surface flow visualization and drag reduction of solid-liquid interface. Various measuring methods have been developed with the rapid development of micro and nano technology. This paper focuses on the measurement of WSS by using nematic liquid crystal coating. A quantitative model is built to describe the relationship between the variations of director orientation and the WSS based on the curvature elasticity theory of liquid crystal. Then an experiment setup is built to verify this model using 5 CB and 7 CB through the optical method. There is good consistence between the theoretical model and experiment results. Finally, the WSS measuring limits and influencing factors are discussed such as the thickness of the liquid crystal layer, the elastic coefficient of the molecule and measurement resolution.

采用液晶涂层测量介质流与壁面间剪切应力的定量模型与试验研究

清华大学,摩擦学国家重点实验室,北京100084

关键词:

A quantitative model and experimental investigations of wall shear stress between solid and gaseous fluid using liquid crystal coating

清华大学,摩擦学国家重点实验室,北京100084

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