Reproducibility of Falling Body Viscometry

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This work investigates the reproducibility of falling body viscometry by developing a new continuous measuring method for pressure ranges up to 8,000 bar, capable of identifying stationary falling conditions. Various influences on the falling body are analyzed, leading to the identification of promising shapes. A numerical flow simulation and coupled adjoint optimization are employed to enhance Stokes flow performance. Utilizing ferritic, corrosion-resistant steel enables inductive velocity detection along the entire measuring length and facilitates active lifting of the falling body. The method is applicable for automated viscosity measurement across a spectrum of fluids, from bio-fuels to hydraulic oil. The innovative measuring principle allows for continuous recording of the falling body's velocity, ensuring the identification of stationary conditions. Analytical and numerical methods reveal that the falling body tends to exhibit large eccentricities within a tube, significantly increasing its fall velocity. Additionally, variations in the falling body geometry demonstrate a notable impact on measurement reproducibility. The adjoint optimized body shows excellent reproducibility for low-viscosity fluids, while for high-viscosity fluids, lateral fins have a minimal effect on flow, enabling concentric falling.