Effective viscosity and elasticity of dynamically jammed region and their role for the hopping motion on dense suspensions

Abstract

We investigate the dynamically jammed region (DJR) induced by an impact in dense suspensions and quantify its effective viscosity and elasticity. We propose a phenomenological model, called the DJR model, that contains the contributions from the effective viscosity and elasticity. We confirm good agreements between the results of the simulation and the DJR model for a free-falling impactor. We also discuss the impact of a foot-spring-body system in dense suspensions to mimic the running on the top of dense suspensions. The foot undergoes multiple rebounds and also hops multiple times due to the spring force and the rigidity of the suspensions. We then apply the DJR model to the foot-spring-body system and reproduces the results of the simulations. We also check the parameter dependences of the hopping motion and found that hopping and multiple rebounds are suppressed as the spring stiffness increases.