[ESPResSo-users] Rigid aspherical object in LB fluid

[Rumen Georgiev - 3ME]

Hello,

I intend to use the LB_GPU package coupled with either the Object-in-Fluid (OIF) or Immersed Boundary Method (IBM) packages and I have several questions regarding ESPResSo's capabilities.

I would like to track the motion of a rigid particle composed of two disks connected with a shaft and immersed in a flowing Lattice Boltzmann fluid. The system is periodic only in the flow direction (say, x) and has stationary planar walls in the other two (y and z) -- essentially, this a rectangular duct geometry. The particle is separated from the z-walls by thin lubrication layers. A full description of the system can be found here [doi:10.1038/ncomms3666]. 

After going through the UG, I have come to a couple of conclusions -- could you please verify them:

1. The UG states that intersecting boundaries are tricky -- could you please elaborate on that? What unphysical effects should one expect?
   
2. Both OIF and IBM place an object with a shape of choice in the LB fluid, however, they are both for soft particles. My guess is that by using the proper parameters of the elasticity moduli the particle will act as a rigid one in both cases.
   
3. The UG suggests the IBM package only supports particles which have the same mass density as the fluid and if one wishes to implement a particle with a different density, the OIF method should be used.
   
4. Since friction between the z-walls and the disks is crucial to recovering the experimentally-known motion of the particle, it seems that OIF is the natural choice, since IBM does not support friction.

Thank you very much for your time!

Best regards,

Rumen Georgiev

Rumen Georgiev  |  Intensified Reaction and Separation Systems  |  Process & Energy  |  3mE  |  TU Delft  |  34 J-0-940  |  Leeghwaterstraat 39, 2628 CB, Delft  |  tel. +316 82 946 879