Integrating Flow Testing and Particle Imaging Advances in Characterising Granular Flows^†

In this study, we explore the intersection of mechanical testing and particle imaging techniques, offering a new perspective on granular material science. We examine a range of flow testers, such as the Schulze shear tester, FT4 powder flow tester, and split-bottom tester, each of which provides valuable insights into how materials respond to compression and shear forces. Simultaneously, we discuss imaging techniques such as refractive index matching, MRI, and X-ray imaging, revealing their capacity to capture the intricate behaviours of particles and flow dynamics at a microscopic level. This combination of macroscopic flow testing and microscopic imaging promises to unlock unprecedented insights into granular materials and complex fluids. Furthermore, we discuss the current challenges in imaging granular flows and recent advances in coupling flow tests with particle imaging.