GeophysicalModelGenerator.jl

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JustPIC ​

JustPIC.jl stores material properties on particles. Once JustPIC is loaded, the geometry routines of GMG accept JustPIC particles in place of a grid. Phases and temperatures are then evaluated at the position of every particle. Interfaces are therefore resolved at particle resolution, rather than at the resolution of the numerical grid, and do not show a staircase pattern.

julia
using GeophysicalModelGenerator, JustPIC

particles = JustPIC.init_particles(backend, nxcell, max_xcell, min_xcell, grid_vel...)
pPhases, pT = JustPIC.init_cell_arrays(particles, Val(2))

pg = particle_grid(particles; length_unit = 1m)     # particle coordinates are in m

add_box!(pPhases, pT, pg; xlim = (0, 500), zlim = (-80, 0),
    phase = LithosphericPhases(Layers = [20, 80], Phases = [1, 2]), T = HalfspaceCoolingTemp(Age = 80))
add_sphere!(pPhases, nothing, pg; cen = (250, 0, -100), radius = 20, phase = ConstantPhase(3))

Particle grid ​

particle_grid collects the active particles once. Every later call reuses it and modifies the particle arrays in place, so build it after init_particles and before the particles move.

  • Units: length_unit is the length of one unit of the particle coordinates, for example 1m, or the characteristic length of a nondimensional model. Geometry parameters are given in km, as everywhere else in GMG.

  • 2D axes: in 2D, the second particle coordinate is the vertical one and corresponds to z in GMG.

  • Temperature: pass nothing instead of a temperature array to set only phases. Passing a thermal structure T without a temperature array is an error.

The following routines are supported: add_box!, add_sphere!, add_ellipsoid!, add_cylinder!, add_layer!, add_polygon!, add_plate!, add_slab!, add_volcano!, add_fault!, add_stripes!, above_surface and below_surface. The last two return a Bool array shaped like the particle CellArrays, which is false for empty particle slots.

Free surface ​

A GMG topography sets the free surface of a JustPIC MarkerChain (2D) or MarkerSurface (3D):

julia
fill_chain_from_vertices!(chain, topo_line; length_unit = 1m)   # topo_line: CartData of size (nx, 1, 1), e.g. from cross_section
set_topo_from_array!(surf, topo; length_unit = 1m)              # topo: CartData of size (nx, ny, 1)

Together with above_surface(pg, topo) for the air phase, this keeps the particles and the free surface consistent with the same topography.