Radiospheres: fast 3D positioning of spherical particles with x-ray radiography

The three dimensional kinematics of spherical particles are a topic of major interest for the mechanical and process engineering scientific community, be they as a model material for granular geomaterials, as particles entrained in fluid flow or as the solid phase in a hydrodynamic suspension. Time-resolved 3D particle tracking is currently only possible in specific conditions: for example x-ray tomography is impossible to apply to these problems because the requirement to rotate the specimen makes phenomena impossible to study considering their rapid evolution in time.

In this project we propose to rally four research labs around a new x-ray radiography-based measurement tool promising to deliver fast 3D particle kinematics for dense assemblies of mono-sized spheres. More precisely, we plan to develop the radioSphere measurement technique, which is currently in the proof-of-concept stage. It allows 3D positioning of spheres of a known size from a single x-ray radiograph and promises to allow unprecedented particle tracking in dense flows in diverse fields. Indeed, the technique is of interest for a number of labs in the Tec21 perimeter (LEGI, LRP, INRAE, 3SR); within the project, simple “demonstrator” experiments will be developed, operated and analysed with scientists in each lab, allowing the technique to be proved (and improved/adapted) and novel measurements to be performed. Scientific breakthroughs related to each demonstrator fall under the category of unprecedented measurements thanks to better time resolution, ability to measure particle kinematics without constraint on the carrier phase parameters (e.g., optical index, viscosity), or ability to resolve kinematics in a very dense collection of particles. Four main demonstrators will be developed in each of the four partner laboratories as illustrated in Fig.1 : Fluidisation of granular bed with different injection rates (LEGI), particle kinematics in a dense suspension (LRP), particle collisions in dense granular flow around an obstacle (INRAE), revealing kinematic fluctuations during lid-driven shear (3SR). A significant part of the project will be related to the writing, testing and documenting of release-quality scientific code, as well as optimising the existing proof-of-concept code for speed and rendering it robust to noise and realistic experimental conditions. A side-project in the post-doc will be to try to develop a simple high speed x-ray camera along the classic lines of scintillator-mirror-camera, because going past the 60Hz detectors currently available on campus is of interest to all parties.