Orateur
Description
We investigate flows involving yield-stress fluids in porous media using a pore-network model, a simplified representation of porous media. Dynamic two-phase flows are considered, where a Newtonian fluid is injected into a medium initially saturated with a yield-stress fluid. In this system, yield stress competes with both capillarity and viscous forces, leading to the appearance of multiple new flow regimes.
A breakthrough criterion is derived and three novel flow regimes are studied: a stable-front
regime, and two invasion patterns that arise from the presence of the yield stress. When the
invading Newtonian fluid is highly viscous, preferential flow paths develop for high yield
stress values and lead to the formation of a column-like invasion pattern. In contrast, for
lower viscosities, a directed tree structure emerges from the branching of the advancing
paths.