2021 MRV Challenge: Results and Comparisons

This presentation is part of the 2021 Magnetic Resonance Velocimetry (MRV) Challenge and represents the combined results from all the participants of the challenge. The objective of this challenge is to benchmark equipment and imaging sequences for obtaining three-dimensional, phase-locked measurements of a flow with periodic unsteadiness. Four research groups have made measurements in the same apparatus comprising a square cross section water channel apparatus with a periodic array of cuboids representing buildings, motivated by applications of turbulent transport in urban areas.  The apparatus that was transferred between the research labs includes detailed flow conditioning to ensure that variations in supply and exit plumbing will limit disruptions to the test section flow. The test was conducted at a Reynolds Number of 15,000 based on the channel hydraulic diameter, and the geometry includes an injector located in the floor of the channel in a building wake which is pulsed between on and off conditions.  The pulsatile nature of the flow lends itself to transient measurements through the injection cycle and ensures strongly three-dimensional flow fields in each set of measurements. This presentation will focus on the results from each team, which will be compared at the injection location and through the downstream building array using velocity field contour plots, iso-surfaces, and quantities derived from the mean velocity components. Similarities and differences will be presented which can provide insight into the opportunities that state of the art MRV provides to researchers.