non-Newtonian flow simulation with mDBC


I have noticed from previous posts that the current version does not support NN fluid simulation based on mdbc.

However, the implementation of partial-slip conditions is crucial for the simulation of high-dense flow, so I am currently also attempting to improve the interfacial conditions for multiphase flow.

I found if I applied the mDBC modification to the NN fluid simulation, a big noise would occur in the density and pressure field:

The issue can be improved if we remove the DDT term (set to 0), but noise still occurs near the boundary. Despite I use the same parameters set equal to the pure water:

Below is the default case study:

It seems that density diffusion term is causing numerical oscillations, but DDT has no issues with NN fluid in DBC scenarios. Why doesn't it work with mDBC?

My preliminary speculation is that the difference may be due to the discrepancy between the density evolution of NN fluid and regular fluid. Although both are calculated based on state equations, it seems that the density field of NN fluid needs to stabilize after a certain number of time iterations. However, I am not sure if this is the key factor affecting the application of mDBC.

Can anyone give some advice, please?

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