Ludwig: multiple GPUs for a fluid lattice Boltzmann application 365
intercept or cut the spherical shell (see Fig. 15.3). Hydrodynamic boundary
conditions are then implemented via the standard approach of bounce-back on
links [7, 11], where the relevant post-collision distribution values are reversed
at the propagation stage with an appropriate correction to allow for the solid
body motion. The exchange of momentum at each link must then be accu-
mulated around the entire particle surface to provide the net hydrodynamic
force and torque on the sphere. The particle motion can then be updated in
a molecular dynamics-like step.
For the CPU implementation, a number of additional MPI communications
are required: (1) to exchange the center position, radius, ...