presence of non-Newtonian fluids is one of the two main
causes of nonlinear behavior during single-phase flow
(inertial effects being the other). Significant advances
have been made in this area during the past few years,
with good progress toward quantitative modeling.
Research in this area has highlighted the limitations of
traditional networks and thus has spurred work on
advanced network-generation techniques and specialized
algorithms for fluid-flow modeling. These developments
are valuable for other types of nonlinear flow modeling.
The images above depict the flow
of a yield-stress fluid in a packed bed. On the left is
the single flow path that is established at the minimum
yield stress (For clarity, the rest of the network
structure is not shown). The subsequent images are at
higher applied pressure gradients, which results in a
larger fraction of the fluid yielding and moving through
the pore space (black color indicates flowing fluid).