search

ludwig-cf / ludwig

A lattice Boltzmann code for complex fluids
https://ludwig.epcc.ed.ac.uk
Other
55 stars 36 forks source link

Cell list restrictions #323

Closed kevinstratford closed 1 month ago

kevinstratford commented 2 months ago

Summary

The cell list restrictions related to the particle extent cf the local domain size are too restrictive for some ellipsoid cases with high aspect ratio.

For example, an ellipsoid with long semi-major axis aligned down a long narrow channel currently fails owing to the constraints in the cross-channel direction.

Solution

In the case of a non-periodic dimension (walls) and no decomposition (mpisz = 1) it should be possible to relax the constraint on at least two cells safely.

For periodic directions, the safety requirement remains live. However, some ability for the user to override this for 'safe' configurations can be considered.

kevinstratford commented 2 months ago

I've relaxed the constraint that two cells are required in a narrow channel. There is an example at

tests/regression/d3q27/serial-elip-s10.inp

This should fix the issue in the case of two narrow directions with walls. However, if one narrow direction is open, something different will be required (pending...).

kevinstratford commented 1 month ago

I am going to leave the issue of the periodic dimension alone for the time being, as it should always be possible to extend the system to a size sufficient to satisfy the constraints of the cell list.