Particles

ERF has the option to include Lagrangian particles in addition to the mesh-based solution. Currently there are two particle types available in ERF: tracer_particles and hydro_particles. The particle functionality is very simple and meant for demonstration. The particles are initialized one per mesh cell in a vertical plane at \(i = 3\) for tracer particles and a horizontal plane at \(k = 23\) for hydro particles. The tracer particles are advected by the velocity field; the hydro particles fall with a velocity determined by gravity minus drag.

However, the AMReX particle data structure is very general and particles may take on a number of different roles in future.

To enable the use of particles, one must set

USE_PARTICLES = TRUE

in the GNUmakefile if using gmake, or add

-DERF_ENABLE_PARTICLES:BOOL=ON \

to the cmake command if using cmake. (See, e.g., Build/cmake_with_particles.sh)

One must also set

erf.use_tracer_particles = 1

and / or

erf.use_hydro_particles = 1

in the inputs file or on the command line at runtime.

Caveat: the particle information is currently output when using the AMReX-native plotfile format, but not when using netcdf. Writing particles into the netcdf files is a WIP.

To see an example of using the particle functionality, build the executable using gmake in Exec/DevTests/ParticlesOverWoA.

To visualize the number of particles per cell as a mesh-based variable, add tracer_particle_count (if you have set erf.use_tracer_particles) and hydro_particle_count (if you have set erf.use_tracer_particles) to the line in the inputs file that begins

erf.plot_vars_1 =