Measurement of Viscosity Using a Long-Period Fiber-Grating-Based Viscometer

This work addresses the comprehensive viscosity measurements and assessment of fluidic materials in the range from 0.01 to 2000 Poises using a fiber optical viscometer with the long-period fiber grating (LPFG) technology. The fluidic materials used and evaluated in this study were AC-20 asphalt cement, four types of silicone oils, and sunflower seed oil. We simultaneously measured the LPFG-induced discharge time and the transmission spectra both in hot air and fluidic materials (other than the AC-20 asphalt) at six different temperatures, i.e., 30, 60, 80, 100, 135, and 170 Celsius. An electromechanical rotational viscometer was also used to measure the viscosities of fluidic materials-the silicone oils and sunflower seed oil at the above six temperatures. Comparative analysis shows that the LPFG-induced discharge time agreed well with the viscosities obtained from the rotational viscometer. The LPFG-based viscometer was capable of measuring the viscosity (discharge time) in the range from 0.12 to 2000 Poises, which is much wider than the viscosity range of a traditional electromechanical rotational viscometer. This fiber-optic LPFG-based viscometer could be proposed and implemented in the field of road and airfield pavement technology such as the viscosity measurements of asphalt cements, emulsified asphalt binders, and other viscous materials. Hopefully, such a highly sensitive viscometer is suitable for use in various fields of applications, such as civil, food, chemical and biological, mechanical, petroleum, and aerospace engineering.