Preprints
https://doi.org/10.5194/esurf-2020-99
https://doi.org/10.5194/esurf-2020-99

  08 Dec 2020

08 Dec 2020

Review status: a revised version of this preprint is currently under review for the journal ESurf.

Rarefied particle motions on hillslopes: 2. Analysis

David Jon Furbish1, Sarah G. W. Williams1, Danica L. Roth2,a, Tyler H. Doane1,b, and Joshua J. Roering2 David Jon Furbish et al.
  • 1Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, Tennessee, USA
  • 2Department of Earth Sciences, University of Oregon, Eugene, Oregon, USA
  • acurrently at: Department of Geology and Geological Engineering, Colorado School of Mines, Golden, Colorado, USA
  • bcurrently at: Department of Earth and Atmospheric Sciences, Indiana University, Bloomington, Indiana, USA

Abstract. We examine a theoretical formulation of the probabilistic physics of rarefied particle motions and deposition on rough hillslope surfaces using measurements of particle travel distances obtained from laboratory and field-based experiments, supplemented with high-speed imaging and audio recordings that highlight effects of particle-surface collisions. The formulation, presented in a companion paper (Furbish et al., 2020a), is based on a description of the kinetic energy balance of a cohort of particles treated as a rarefied granular gas, and a description of particle deposition that depends on the energy state of the particles. Both laboratory and field-based measurements are consistent with a generalized Pareto distribution of travel distances and predicted variations in behavior associated with the balance between gravitational heating due to conversion of potential to kinetic energy and frictional cooling due to particle-surface collisions. For a given particle size and shape these behaviors vary from a bounded distribution representing rapid thermal collapse with small slopes or large surface roughness, to an exponential distribution representing approximately isothermal conditions, to a heavy-tailed distribution representing net heating of particles with large slopes. The transition to a heavy-tailed distribution likely involves an increasing conversion of translational to rotational kinetic energy leading to larger travel distances with decreasing effectiveness of collisional friction. This energy conversion is strongly influenced by particle shape, although the analysis points to the need for further clarity concerning how particle size and shape in concert with surface roughness influence the extraction of particle energy and the likelihood of deposition.

David Jon Furbish et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

David Jon Furbish et al.

David Jon Furbish et al.

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