(10)
where μf is the fluid viscosity.
The Kozeny–Carman relation (Kozeny et al., 1927; Carman 1939) was used
to estimate the permeability. Two-way coupling was accomplished by
updating the permeability coefficient information for each fluid element
and updating the fluid velocity field of each discrete element. The
permeability of each fluid element was calculated from the porosity of
the PFC3D model, and the calculation is given by Eq. (11),