落球法测量液体黏滞系数的实验探究  

EXPERIMENTAL RESEARCH ON MEASURING LIQUID VISCOSITY COEFFICIENT BY FALLING BALL METHOD

作　　者：宛天健 刘立英[1] 段博方 原安娟[1] 王吉有[1] WAN Tianjian;LIU Liying;DUAN Bofang;Yuan Anjuan;WANG Jiyou(Department of Science,Beijing University of Technology,Beijing 100124)

机构地区：[1]北京工业大学理学部,北京100124

出　　处：《物理与工程》2022年第4期171-177,共7页Physics and Engineering

基　　金：北京工业大学教育教学研究课题(ER2022SJB11);北京工业大学星火基金项目(XH-2022-05-08)。

摘　　要：黏滞系数是描述液体内摩擦性质的一个重要物理量,在工业、农业以及医学方面有着重要的应用。在黏滞系数的诸多测量方法中,传统的落球法现象直观,被广泛应用于大学物理实验。然而,目前落球法常用的秒表计时或光电门计时都会代来很大的不确定度。对此,我们提出了全新的测量理念——低速摄影法。与传统光电法以及CCD法不同,我们放慢视角,设置较长的曝光时间,用每张图片记录下小球“单位时间”下落轨迹。基于轨迹长度以及曝光时间等参数,可以直接算得小球匀速下落速度,进而求得黏滞系数,具有响应快、精度高、装置简的优势。进一步的,基于低速摄影法,实验观测到高速下落的小球受涡流、压阻作用而旋转、偏离竖直线的现象,并结合数据与模型探讨了其对结果的影响。分析表明,落球法测量黏滞系数实验中可通过小球密度和半径的调节来控制落球速度,有效避免涡旋和压阻带来的误差。Viscosity coefficient is an important physical quantity to describe the internal friction properties of liquid.It has important applications in industry,agriculture,and medicine.Among many ways of viscosity coefficient measurement,the traditional falling ball method is intuitive and widely used in college physics experiments.However,two common program to measure the dropping ball,timing by stopwatch or photoelectric gates,will cause a large uncertainty.In pursuit of an ideal method,we came up with a brand-new concept—Low Speed Photography Measurement.Different from the method of photoelectric gates or CCD,we adopt to a slow perspective.By using a low shutter speed,a single exposure will record a trajectory of the ball.According to shutter speed and length of a certain trajectory,the uniform falling speed of the ball can be calculated directly,and then the viscosity coefficient the liquid can be obtained.Compared to traditional method,Low Speed Photography Measurement shows extraordinary superiorities in speed,accuracy,and simplicity.Furthermore,based on this method,the phenomenon that the small ball falling at high speed rotates and deviates from the vertical line under the action of eddy current and pressure drag is observed experimentally,and its influence on the results is discussed combined with the data and model.The analysis shows that in the experiment of measuring viscosity coefficient by falling ball method,the falling ball speed can be controlled by adjusting the density and radius of the small ball,so as to effectively avoid the errors caused by vortex and pressure drag.

关 键 词：黏滞系数 摄影法 落球法 曝光时间 像素 

分 类 号：O552.42[理学—热学与物质分子运动论]