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Measurement of viscosity of highly viscous non-Newtonian fluids by means of ultrasonic guided waves

机译：超声导波法测量高粘度非牛顿流体的粘度

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In order to perform monitoring of the polymerisation process, it is necessary to measure viscosity. However, in the case of non-Newtonian highly viscous fluids, viscosity starts to be dependent on the vibration or rotation frequency of the sensing element. Also, the sensing element must possess a sufficient mechanical strength. Some of these problems may be solved applying ultrasonic measurement methods, however until now most of the known investigations were devoted to measurements of relatively low viscosities (up to a few Pa s) of Newtonian liquids. The objective of the presented work is to develop ultrasonic method for measurement of viscosity of high viscous substances during manufacturing process in extreme conditions. For this purpose the method based on application of guided Lamb waves possessing the predominant component of in-plane displacements (the S_0 and the SH_0 modes) and propagating in an aluminium planar waveguide immersed in a viscous liquid has been investigated. The simulations indicated that in the selected modes mainly inplane displacements are dominating, therefore the attenuation of those modes propagating in a planar waveguide immersed in a viscous liquid is mainly caused by viscosity of the liquid. The simulation results were confirmed by experiments. All measurements were performed in the viscosity standard Cannon N2700000. Measurements with the S_0 wave mode were performed at the frequency of 500 kHz. The SH_0 wave mode was exited and used for measurements at the frequency of 580 kHz. It was demonstrated that by selecting the particular mode of guided waves (S_0 or SH_0), the operation frequency and dimensions of the aluminium waveguide it is possible to get the necessary viscosity measurement range and sensitivity. The experiments also revealed that the measured dynamic viscosity is strongly frequency dependent and as a characteristic feature of non-Newtonian liquids is much lower than indicated by the standards. Therefore, in order to get the absolute values of viscosity in this case an additional calibration procedure is required. Feasibility to measure variations of high dynamic viscosities in the range of (20-25,000) Pa s was theoretically and experimentally proved. The proposed solution differently from the known methods in principle is more mechanically robust and better fitted for measurements in extreme conditions.
机译：为了监视聚合过程，必须测量粘度。但是，在非牛顿高粘度流体的情况下，粘度开始取决于传感元件的振动或旋转频率。而且，传感元件必须具有足够的机械强度。使用超声波测量方法可以解决其中的一些问题，但是直到现在，大多数已知的研究都致力于牛顿液体的相对较低粘度（高达几Pa s）的测量。提出的工作的目的是开发一种超声波方法，用于在极端条件下的制造过程中测量高粘度物质的粘度。为此，已经研究了基于施加导引的兰姆波的方法，该兰姆波具有平面内位移的主要成分（S_0和SH_0模式）并在浸没在粘性液体中的铝平面波导中传播。模拟表明，在选定的模式中，平面内的位移占主导，因此，在浸没在粘性液体中的平面波导中传播的那些模式的衰减主要是由液体的粘度引起的。通过实验验证了仿真结果。所有测量均在粘度标准Cannon N2700000中进行。使用S_0波模式的测量是在500 kHz的频率下进行的。退出SH_0波模式，并用于580 kHz频率的测量。结果表明，通过选择特定的导波模式（S_0或SH_0），铝波导的工作频率和尺寸，可以获得必要的粘度测量范围和灵敏度。实验还表明，测得的动态粘度强烈依赖于频率，并且非牛顿液体的特征远低于标准所指示的粘度。因此，在这种情况下，为了获得粘度的绝对值，需要额外的校准程序。从理论上和实验上证明了测量（20-25,000）Pa s范围内高动态粘度变化的可行性。所提出的解决方案在原理上与已知方法不同，其在机械上更坚固，并且更适合极端条件下的测量。

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