Graduate Program in Acoustics, The Pennsylvania State University, University Park, PA 16802, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Jul;57(7):1612-20. doi: 10.1109/TUFFC.2010.1591.
This paper presents an empirical method for measuring the viscosity of mineral oil. In a built-in pipeline application, conventional ultrasonic methods using shear reflectance or rheological and acoustical phenomena may fail because of attenuated shear wave propagation and an unpredictable spreading loss caused by protective housings and comparable main flows. The empirical method utilizing longitudinal waves eliminates the unknown spreading loss from attenuation measurements on the object fluid by removing the normalized spreading loss per focal length with the measurement of a reference fluid of a known acoustic absorption coefficient. The ultrasonic attenuation of fresh water as the reference fluid and mineral oil as the object fluid were measured along with the sound speed and effective frequency. The empirical equation for the spreading loss in the reference fluid is determined by high-order polynomial fitting. To estimate the shear viscosity of the mineral oil, a linear fit is applied to the total loss difference between the two fluids, whose slope (the absorption coefficient) is combined with an assumed shear-to-volume viscosity relation. The empirical method predicted the viscosities of two types of the mineral oil with a maximum statistical uncertainty of 8.8% and a maximum systematic error of 12.5% compared with directly measured viscosity using a glass-type viscometer. The validity of this method was examined by comparison with the results from theoretical far-field spreading.
本文提出了一种测量矿物油粘度的经验方法。在内置管道应用中，由于剪切波传播的衰减和保护外壳以及可比主流引起的不可预测的扩散损耗，传统的使用剪切反射率或流变和声学现象的超声波方法可能会失效。利用纵波的经验方法通过测量已知声吸收系数的参考流体来消除归一化每焦距扩散损耗，从而从对象流体的衰减测量中消除未知的扩散损耗。测量了淡水作为参考流体和矿物油作为对象流体的超声波衰减、声速和有效频率。参考流体中的扩散损耗的经验方程通过高阶多项式拟合确定。为了估计矿物油的剪切粘度，将两种流体之间的总损耗差进行线性拟合，其斜率（吸收系数）与假设的剪切-体积粘度关系相结合。与使用玻璃型粘度计直接测量的粘度相比，经验方法预测了两种类型的矿物油的粘度，最大统计不确定度为 8.8%，最大系统误差为 12.5%。通过与远场扩散的理论结果进行比较，验证了该方法的有效性。
