Impact-induced hardening in dense frictional suspensions

Abstract

By employing the lattice Boltzmann method, we perform simulations of dense suspensions under impacts, which incorporate the contact between suspended particles as well as the free surface of the suspension. Our simulation for a free falling impactor on a dense suspension semi-quantitatively reproduces experimental results, where we observe rebounds of the impactor by the suspension containing frictional particles for high speed impact and high volume fraction shortly after the impact before subsequently sinking. We observe that the response depends on the radius of the impactor, which leads to fitting our simulation data to a phenomenological model based on the Hertzian contact theory. When the rebound takes place, percolated force chains are formed by the frictional contacts between suspended particles. Furthermore, persistent homology analysis is used to elucidate the significance of the topological structure of the force chains, where the total persistence of connected components correlates with the force supporting the impactor.