Reynolds Stress Tensor Measurements In A Shear-Thinning Fluid Using Magnetic Resonance Velocimetry: A Parameter Study With The FDA Benchmark Nozzle
K. John, C. Wüstenhagen, M. Bruschewski, S. Grundmann
Institute of Fluid Mechanics, University of Rostock, Germany
Compared to refractive index matching in laser optical measurement techniques, magnetic resonance velocimetry (MRV) is assumed to be comparatively robust to changes in fluid composition when the principal components of the mixture provide a measurable MRI signal. In previous studies, MRV measurements were performed with different mixtures of water and glycerol, and no significant errors arose regardless of the mixing ratio. MRV is therefore proposed as a promising method for providing experimental data for a wide range of fluids that may also replicate different viscosity models. However, MRV can suffer from so-called chemical shift artifacts caused by slight variations in resonance frequency of differently bound hydrogen protons. These effects may arise when additional components are added to the flow medium. In this study, the ability of MRV to measure different flow mixtures is investigated. The long-term goal is to provide comprehensive experimental validation data for viscosity models in numerical simulations. Measurements were performed in stationary fluid samples as well as in flow measurements at the sudden expansion of the FDA benchmark nozzel. It is shown that MRV can provide reliable results for a Newtonian fluid and a shear-thinning fluid.