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published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Current commonly use viscosity measurement techniques cannot be used for all types of fluids. For fluids in the under cooled region a new method of measuring the viscosity is required. A process of viscosity measurement, by measuring the speed of droplet coalescence in a microgravity environment, was developed. This paper analyses validation experiments performed on the International Space Station. Four experiments were analyzed. Two of the experiments provided results consistent with the known value for the viscosity. One of the experiments did not provide sufficient data for analysis. The final experiment had possible errors due to the experimental setup. The resulting data from these experiments demonstrated that the method is feasible. However, more experiments are needed to fully verify the process.

The goal of this research is to measure viscosity via the analysis of amplitude response of a piezo driven vibrating cantilevers partially immersed in a viscous medium. As a driving frequency is applied to a piezoceramic material, the external forces acting on the system will affect its maximum amplitude. This thesis applies this principle through experimental and analytical analyses of the proportional relationship between viscosity and the amplitude response of the first natural frequency mode of the sinusoidal vibration. Currently, the few cantilever-based viscometer designs that exist employ resonant frequency response as the parameter by which the viscosity is correlated. The proposed piezoelectric viscometer employs amplitude response in lieu of resonant frequency response. The goal of this aspect of the research was to provide data confirming amplitude response as a viable method for determining viscosity. A miniature piezoelectric plate was mounted to a small stainless-steel cantilever beam. The tip of the cantilever was immersed within various fluid test samples. The cantilever was then swept through a range of frequencies in which the first frequency mode resided. The operating principle being as the viscosity of the fluid increases the amplitude response of cantilever vibration will decrease relatively. What was found was in fact an inversely exponential relationship between dynamic viscosity and the cantilever beam's vibrational amplitude response. The experiment was performed using three types of cantilevers as to experimentally test the sensitivity of each.