Real-time imaging of granular dynamics

The dynamics of granular materials govern natural phenomena ranging from earthquakes, to avalanches to landslides and are critical for a variety of industrial applications. Our fundamental physical understanding of granular dynamics, however, is still incomplete. One major challenge towards a better understanding of granular dynamics is the difficulty to obtain spatially and temporally resolved measurements of particle dynamics from the interior of 3D granular systems. Magnetic resonance imaging (MRI) is able to measure a variety of relevant system properties, however, one of the largest limitation so far has been the rather low temporal resolution. Here we report our recent developments, an MRI methodology that increases the temporal resolution of phase contrast velocity encoded imaging of granular dynamics by more than four orders of magnitude, effectively advancing MRI of granular dynamics from temporally averaged to real-time imaging [1]. The advances are enabled by an interplay of engineered MR signal sources, timeefficient single shot readouts and radiofrequency (RF) hardware developments and provide insight into hitherto unknown facets of dynamic granular behavior (Fig.1). We are confident that the methodology will be useful for studying a variety of dynamic granular systems in the fields of process engineering, granular physics and geophysics.