The optical viscometer based on the vibrating fiber partially submerged in fluid

The vibrating fiber partially submerged in fluid has been shown to be an effective device for the viscosity sensing. In this study, small vibrational amplitude of the fiber (<1.0 μm) is detected by the optical method utilizing a forward light scattering pattern. An analytical solution of the partially submerged fiber vibration with damping has been found and results agree well with experimental data in the wide ranges of the different liquids and depths. It has been shown that variations of the maximum vibrational amplitude (MVA) and the bandwidth depend linearly on (ρlμl)1/2 and split over the liquid depth. Based on the results a simple way for the viscosity extraction from both the MVA and the bandwidth has been suggested and an explicit formula for the achievable accuracy of the viscosity sensing has been derived. Experiments have confirmed the method of the viscosity extraction.