拉脱法测表面张力系数测量值不稳定的原因分析与验证  

Analysis and verification of the instability of surface tension coefficient measurement by pull-off method

作　　者：陶然[1] 张辰 张雅男[2] 芮云军[1] TAO Ran;ZHANG Chen;ZHANG Yanan;RUI Yunjun(Department of Physics,Nanjing Tech University,Nanjing 211816,China;Engineering Training Center,Nanjing University of Information Science&Technology,Nanjing 210044,China)

机构地区：[1]南京工业大学物理系,江苏南京211816 [2]南京信息工程大学工程训练中心,江苏南京210044

出　　处：《物理实验》2023年第3期36-42,共7页Physics Experimentation

基　　金：国家自然科学基金项目资助(No.61704079);江苏省大学生创新训练计划重点(国家级)项目资助(No.202210291079Z)。

摘　　要：拉脱法测量液体表面张力系数实验中,采用薄壁(0.6 mm)吊环和标准(1.0 mm)吊环,测量值相对稳定;但对于较厚壁(1.5,2.0,2.5 mm)吊环,每次测量值差别很大.通过手机拍摄视频,对不同时刻的液膜形状进行理论和实验分析,发现测量值不稳定的主要原因是颈缩突变,即拉伸过程中,液膜收缩从吊环外壁突变到内壁的程度不同,导致后续液膜断裂点的位置相差非常大,造成测量值的起伏不定.因此需将吊环平均直径替换为断裂时的液膜直径,对测量值进行修正.结果表明:修正后的表面张力系数与理论值的误差减小到了4.0%以内,验证了理论分析的正确性.In the measurement of liquid surface tension coefficient by pull-off method,the measured values were relatively stable for the thin-walled or standard(0.6 or 1.0 mm)circular rings,but the measured values were very different for the thick-walled(ranging from 1.5 to 2.5 mm)rings.Theoretical and experimental analysis of the liquid film shape at different moments were carried out by taking pictures with a smartphone.It was found that the main reason for instability of the measured values was the“abrupt neck-shrinkage”.During the pulling process,the liquid film shranked abruptly from the outer wall of the ring to the inner wall at a different degree,resulting in a large location difference in the subsequent liquid film breaking point and then for the instability of the measured values.Therefore,the measured value should be corrected by replacing the average diameter of the ring with the diameter of the liquid film at breaking point.The results showed that the error of the corrected surface tension coefficient was reduced to within 4.0%compared with the theoretical value,which verified the correctness of the theoretical analysis.

关 键 词：拉脱法 表面张力系数 吊环厚度 液膜重力 颈缩突变 断裂点直径 

分 类 号：O351.1[理学—流体力学]