Early-stage impact dynamics in dense suspensions of millimeter-sized particles

We investigate the early-stage impact dynamics in dense suspensions composed of millimeter-sized particles. While traditional models based on the Stokes flow are typically applicable to suspensions of micrometer-sized particles, their validity for larger particles remains uncertain. Through controlled impact experiments, we examine the maximum drag force Fmax acting on a projectile as a function of impact speed u0. We have successfully conducted experiments using these suspensions and confirmed the relation Fmax∼u03/2 for relatively large u0 as observed in the previous studies of suspensions of micrometer-sized particles. Our results demonstrate that the floating model—equivalent to the viscous model—successfully captures the early-stage dynamics even in suspensions with larger particles. This finding suggests that viscous-dominated behavior persists under certain conditions, extending the applicability of the floating model or the viscous model to new regimes. Our work provides experimental validation for theoretical predictions and contributes to a deeper understanding of impact-induced responses in dense suspensions.