[richpaj]

Particle-Locking in DieselFoam (parallel operation)

Recently, we experienced the situation where a particle appeared to be 'locked'
at a particular site in the mesh under consideration with the result that the
associated spray computation was completely stalled (as denoted by the final message
"Evolving Spray").

Closer inspection of the mesh at the relevant point revealed that the site coincided
with the common vertex of several tetrahedra and, additionally, lay in
the vicinity of the interface between two processor patches.

There then resulted an infinite loop in which the particle was continuously registered
for "transfer" between two processor patches at the end of each update
in the spray (cf. CCloud.C).


In order to circumvent the situation then, it was decided to (approximately) return the particle to its
position at the end of the previous (CFD) timestep, perturb that starting point and then
recompute the trajectory. More precisely, all the characteristic values of the particle
should be returned to their initial values but, given that this is likely to be a rare eventuality
no significant error is expected by not doing so, at present.

I wonder if this has been observed before? Or if a simpler solution exists to this problem?

Regards,

Richard Kenny.

P.S.. The working mesh is "fixed" and nothing at present can be done about that,
furthermore checkMesh records no holes in the mesh.