# Ultraslow settling kinetics of frictional cohesive powders Source: [Ultraslow settling kinetics of frictional cohesive powders]() Collection index: [llms.txt]() Data updated: 2025-10-25T04:42:01.720Z Authors: Kai Nan, Robert S. Hoy Published: 2022-12-09T18:13:08.000Z ## Abstract Using discrete element method simulations, we show that the settling of frictional cohesive grains under ramped-pressure compression exhibits strong history dependence and slow dynamics that are not present for grains that lack either cohesion or friction. Systems prepared by beginning with a dilute state and then ramping the pressure to a small positive value $P\_{\\rm final}$ over a time $\\tau\_{\\rm ramp}$ settle at packing fractions given by an inverse-logarithmic rate law, $\\phi\_{\\rm settled}(\\tau\_{\\rm ramp}) = \\phi\_{\\rm settled}(\\infty) + A/\[1 + B\\ln(1 + \\tau\_{\\rm ramp}/\\tau\_{\\rm slow})\]$. This law is analogous to the one obtained from classical tapping experiments on noncohesive grains, but crucially different in that $\\tau\_{\\rm slow}$ is set by the slow dynamics of structural void stabilization rather than the faster dynamics of bulk densification. We formulate a kinetic free-void-volume theory that predicts this $\\phi\_{\\rm settled}(\\tau\_{\\rm ramp})$, with $\\phi\_{\\rm settled}(\\infty) = \\phi\_{\\rm ALP}$ and $A = \\phi\_{\\rm settled}(0) - \\phi\_{\\rm ALP}$, where $\\phi\_{\\rm ALP} \\equiv .135$ is the \`\`adhesive loose packing'' fraction found by Liu \\textit{et al.} \[W.\\ Liu, Y.\\ Jin, S. Chen, H.\\ A.\\ Makse and S.\\ Li, \\textit{Soft Matt.} \\textbf{13}, 421 (2017)\]. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()