Non-Newtonian flows include several regimes, depending on the solid concentration of the fluid and, for higher concentration mixtures, the grain size of the solids. It is helpful to think of this classification as a hierarchy. In general, as concentration increases (and the solid component coarsens) the fluid passes through five classifications:

  1. Hyperconcentrated Flow
  2. Mud and debris flow
  3. Clastic Flow

Dividing a continuum into a classification imposes artificial boundaries and mathematical discontinuities. Non-Newtonian flows are complicated because they do not form a continuum on a single axis. These classifications are somewhat arbitrary and the terminology in the non-Newtonian literature

The four classes of non-Newtonian flows in the Debris library, the criteria used to separate them, and the model used to simulate them are summarized in the table and figure below.

Table: Non-Newtonian flow classifications, thresholds, and the model used to simulate them.

Classification

Model

Condition

Hyperconcentrated

Bingham

Cv>30%

Mud and Debris Flow

Turbulent- Quadratic
Herschel-Bulkley

Cv>60%

Snow Avalanche

Voellmy


Clastic

Mohr-Coulomb

Ns>0.1


Classification, processes, conceptual model, and rheological model of the four non-Newtonian flow types in the Debris Library.