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TY  - THES
AU  - Rückert, Marcel
TI  - Reproducibility of falling body viscometry
VL  - 113
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Düren
M1  - RWTH-2023-06683
SN  - 978-3-8440-9077-2
T2  - Reihe Fluidtechnik / D
SP  - 1 Online-Ressource : Illustrationen, Diagramme
PY  - 2023
N1  - Druckausgabe: 2023. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, RWTH Aachen University, 2023
AB  - The need to increase efficiency is pushing the limits to extreme conditions. Elevated loads by the increase of operating pressure or speed as well as new materials enhance the requirements on fluids as a design element. Viscosity, as the primary factor influencing hydrostatic and dynamic fluid properties, plays a decisive role. Particularly at high operating pressures, viscosity can increase by several orders of magnitude. It is therefore of great interest to be able to determine the viscosity over the entire operational range. In this work, the reproducibility of falling body viscometry is investigated. For this purpose, a new continuous measuring method for pressure ranges up to 8,000 bar is developed, which is able to identify stationary falling conditions. In an analysis all influences acting on the falling body are investigated and promising falling body shapes are identified. With the aid of a numerical flow simulation and coupled adjoint optimisation, a falling body is developed for increased Stokes flow performance. By using a ferritic, corrosion-resistant steel, an inductive velocity detection over the complete measuring length as well as an active lifting of the falling body is made possible. The newly developed method is suitable for the automated viscosity measurement of high- as well as low-viscosity fluids and thus covers the range from bio-fuels to hydraulic oil. Due to the innovative measuring principle, the velocity of the falling body can be continuously recorded and thus stationary conditions can be identified. By means of analytical and numerical methods, it can be shown that a falling body tends towards large eccentricities during the fall in a tube, which significantly increases its fall velocity. Furthermore, a variation of the falling body geometry shows that the falling body shape has a significant influence on the reproducibility of the measurements. The adjoint optimised body provides very good reproducibility and is suitable for the use with low-viscosity fluids. For high viscosity fluids it can be shown that fins on the lateral surface of the falling body have a small influence on the flow and a concentric fall can be realised.
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
DO  - DOI:10.18154/RWTH-2023-06683
UR  - https://publications.rwth-aachen.de/record/961211
ER  -