Insights into the sticking probability of volcanic ash particles from laboratory experiments.

Although the characterization of the sticking and aggregation probability is essential to the description of volcanic ash dispersal and sedimentation, there is still no general model describing the sticking probability of volcanic ash. Experiments of dry particle-plate collisions in an enclosed box were carried out to characterize quantitatively the sticking efficiency of volcanic particles and silica beads in a limit case scenario where the mass of one of the particles is much greater than the others. Silica beads and volcanic particles from a Sakurajima Vulcanian eruption were filmed impacting a glass plate with a High-Speed Camera. The sticking probability is calculated from an equation depending on the particle diameter, impact velocity, and two experimental parameters (a, q). Particle size was found to dominantly control the sticking probability, with small particles more likely sticking on the glass plate than large particles. These experiments represent a significant step forward in the quantification of the sticking efficiency of fine volcanic ash (< 63 μm).