To everyone who is familiar with resolved cfdemSolverIB

Hi, everyone,
I faced a paper in the featured work part on the cfdem website:
https://www.cfdem.com/featured-work
which is:
"Fully resolved simulations of particle-laden viscoelastic fluids using an immersed boundary method"
The question is how it is possible to use cfdemSolverIB method for a non-Newtonian fluid? I think someone should answer my question as I faced some non-newtonian papers using cfdemSolverIB. However, this solver just has been modified for Newtonian rheology!
Please help me to find it out.
Cheers,
Mohammad