Pressure driven flow of collodial suspensions

Hi everyone

I am new to both LAMMPS and this forum so please move this post if it does not belong here.

Currently I am trying to determine if there is in built functionality within the existing LAMMPS packages for pressure driven flow of colloidal suspensions, which takes into account hydrodynamic and interparticle forces (eg; particle collision). For a bit of context, the system I am studying involves carbon particles (roughly 1 micron in diameter) suspended in an electrolyte solution being pumped through a square channel of 10x10x50┬Ám at various volume fractions.

I have previously modelled this using the granular package and adding forces on the particles to represent the mean pressure applied, with fixed particles representing the walls of the channel. However, upon reviewing studies I have found that this is likely to give the incorrect velocity profile of the flow, which should be somewhat more blunted (figure 4 b, Ref. [1]). I am now looking at trying to implement equation 11 from reference [1] below which captures both hydrodynamic and non-hydrodynamic forces to determine evolution of particle positions.
(Where Fo is non hydrodynamic forces, is the average suspension velocity, R is the tensor capturing hydrodynamic forces for superscript I - particles and w - wall)

image

My question is, is there a package or hybrid between packages which I can use to implement equation 11 already existing? I have not had any luck diving through the forums so far to see if anyone else has done this previously.

Looking at the existing packages it looks to me that pair_style lubricate is able to calculate the hydrodynamic portion of this equation, but not the non-hydrodynamic.

Sorry for a long winded first post, and thank you for any suggestions!

References:
[1] Nott, P. R., & Brady, J. F. (1994). Pressure-driven flow of suspensions: simulation and theory. Journal of Fluid Mechanics, 275 (https://authors.library.caltech.edu/11423/1/NOTjfm94.pdf)

Unfortunately, your research topic is something that is not very common in the LAMMPS community, so there is little experience that you can lean on.

A couple of general comments:

  • your kind of two-tier system could possibly also be simulated with a CFD-DEM coupling approach. Check out the LIGGGHTS software for which a coupling to OpenFOAM exists
  • there are a few meso-scale models implemented in LAMMPS, but I cannot say which is suitable. Since your system is rather unusual, probability is not in your favor.
  • the publication your are referring to is a few years old (in fact, it predates the original LAMMPS paper). It may be worth surveying the literature if people have developed alternate approaches for similar systems or whether there are publications citing this paper that do have used an open source MD software that you can use or whether there is a LAMMPS add-on package that is just not submitted to be included in the LAMMPS distribution.

Axel.