Reynolds stress tensor and velocity measurements in technical flows by means of magnetic resonance velocimetry Data acquisition in the flow field behind the sudden expansion of the FDA benchmark nozzle and identification of systematic errors

Magnetic Resonance Velocimetry (MRV), an imaging method based on Magnetic Resonance Imaging (MRI), enables the measurement of flow parameters such as the velocity and the Reynolds Stress Tensor (RST) in complex structures without optical or physical access to the flow field. Several previous studies investigated the application of MRV velocity measurement in technical flows and obtained results that agreed well with reference data. However, only a few studies have investigated RST measurements using MRV beyond medical applications, and even though the qualitative results were promising, further work is required to establish this method. This study demonstrates the application of two-dimensional three-component (2D3C) velocity and six-component (2D6C) RST measurements in the flow field behind the sudden expansion of a scaled replica of the FDA benchmark nozzle. Particle Image Velocimetry (PIV) data accessible from an interlaboratory study was used for comparison. Furthermore, two different orientations of the imaging plane were measured to investigate the effect of the imaging orientation on the results. The measurement uncertainty of the mean axial velocity is 1.2 % related to the bulk velocity. The RST results agree well with the PIV data, but quantitative deviations occur in the areas where the influence of systematic errors was expected. Comparing different imaging orientations demonstrates that the sequence design affects the quantitative results of the measurement.