Local Rheology Relation with Variable Yield Stress Ratio across Dry, Wet, Dense, and Dilute Granular Flows

Research output: Contribution to journalArticle


Dry, wet, dense, and dilute granular flows have been previously considered fundamentally different and thus described by distinct, and in many cases incompatible, rheologies. We carry out extensive simulations of granular flows, including wet and dry conditions, various geometries and driving mechanisms (boundary driven, fluid driven, and gravity driven), many of which are not captured by standard rheology models. For all simulated conditions, except for fluid-driven and gravity-driven flows close to the flow threshold, we find that the Mohr-Coulomb friction coefficient μ scales with the square root of the local Péclet number Pe provided that the particle diameter exceeds the particle mean free path. With decreasing Pe and granular temperature gradient M, this general scaling breaks down, leading to a yield condition with a variable yield stress ratio characterized by M.


  • Thomas Pähtz
  • Orencio Durán
  • David N. De Klerk
  • Indresan Govender
  • Martin Trulsson
External organisations
  • Texas A and M University
  • University of Cape Town
  • University of KwaZulu-Natal
  • Zhejiang University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Fluid Mechanics and Acoustics
Original languageEnglish
Article number048001
JournalPhysical Review Letters
Issue number4
Publication statusPublished - 2019 Jul 24
Publication categoryResearch