Configuration Files¶

gFlex can be driven by a YAML configuration file rather than (or alongside) the programmatic Python API. Pass the file path to the gflex CLI or to an F1D / F2D constructor. The file must have a .yaml or .yml extension.

Parameters¶

`mode` section¶

dimension

1 or 2. Selects a 1-D (profile) or 2-D (map-view) flexural solution.

method

Solution method:

fd — Finite Difference. Supports spatially variable elastic thickness. Requires a grid (dx, and dy in 2-D).
fft — Spectral (Fast Fourier Transform). Requires scalar (uniform) \(T_e\). Spectrally accurate and fast. When all boundary conditions are periodic the domain tiles exactly; for any other boundary condition the load is zero-padded by \(4\alpha\) on each side, approximating the no_outside_loads condition (the default when BCs are unset). Setting only some BCs to periodic triggers a UserWarning and falls back to zero-padding. In-plane stresses (\(\sigma_{xx}\), \(\sigma_{yy}\), \(\sigma_{xy}\)) are supported.

Added in version 1.4.0.
sas — Superposition of Analytical Solutions. Constant elastic thickness only; fast and analytically exact.
sas_ng — SAS on an unstructured point set (NG = “no grid”). Load and output locations are arbitrary (x, q0) or (x, y, q0) columns; see loads below.

`parameter` section¶

youngs_modulus

Young’s modulus \(E\) [Pa]. Typical lithospheric value: 65 GPa (6.5e10).

poissons_ratio

Poisson’s ratio \(\nu\) [dimensionless]. Typical value: 0.25.

gravitational_acceleration

Gravitational acceleration \(g\) [m s⁻²]. Earth standard: 9.8.

mantle_density

Density of the mantle \(\rho_m\) [kg m⁻³]. Typical value: 3300.

infill_material_density

Density of the material that fills (or vacates) the flexural depression \(\rho_\text{fill}\) [kg m⁻³]. Common values:

0 — air (no infill)
1030 — seawater
2000–2700 — sediment

If the infill density varies spatially (e.g., at a subsiding shoreline that progressively floods), iterate externally: flex, update the inundation mask, re-flex, repeat.

`input` section¶

loads

Path to the load file.

Gridded methods (FD, SAS): a space-delimited array of surface normal stresses [Pa] (\(\rho g h\)). Grid cell area (\(\Delta x \times \Delta y\)) is applied internally to convert stress to force.
SAS_NG: a space-delimited file with columns (x, q0) in 1-D or (x, y, q0) in 2-D, where q0 is a point force [N].

Paths are resolved relative to the directory containing the configuration file.

elastic_thickness

Elastic thickness [m]. Either a scalar value or a path to a space-delimited array. Arrays are required for FD solutions with spatially variable Te. Use pad_domain() to extend a variable-Te grid with a smooth boundary buffer before running (works for both 1-D and 2-D; scalar Te is also supported).

xw, yw

(SAS_NG only) Vectors of x (and y for 2-D) coordinates at which to evaluate deflection. If omitted, deflection is evaluated at the load points.

`output` section¶

deflection_out

Path for writing deflection output as a space-delimited ASCII file. Leave blank to suppress file output.

plot

Controls inline plotting after the run:

q — plot the applied load.
w — plot the deflection.
both — deflection and load in separate subplots.
combo — (1-D only) deflection with the load overlaid.

Any other value (or blank) suppresses plotting.

`numerical` section¶

grid_spacing_x

Grid cell size in the x-direction [m].

boundary_condition_west, boundary_condition_east

Boundary conditions on the west and east edges.

For FD: zero_displacement_zero_slope (alias clamped), zero_displacement_zero_moment (alias pinned), zero_moment_zero_shear (alias free), zero_slope_zero_shear (alias mirror), no_outside_loads (alias infinite), or periodic. When no_outside_loads is set on an FD edge, the solver automatically pads the domain by one flexural wavelength, applies a clamped outer boundary, solves, and crops w back to the original domain — the padding is invisible to the caller. See Boundary Conditions for the physical meaning of each and guidance on choosing.

Added in version 2.0.0: zero_displacement_zero_moment (alias pinned) and no_outside_loads (alias infinite) are available as FD boundary conditions.

For SAS / SAS_NG: no_outside_loads is always assumed (the analytical solution is inherently infinite-plate); leave blank or set explicitly.

Note

The v1.x PascalCase strings ("0Displacement0Slope", "0Moment0Shear", "Mirror", etc.) now raise ValueError in v2.0. Replace them with the lowercase canonical forms above. See Boundary Conditions for the full mapping.

Note

Added in version 1.4.0.

In-plane stresses (\(\sigma_{xx}\), \(\sigma_{yy}\), \(\sigma_{xy}\) [Pa]) cannot be set from a configuration file. They must be assigned programmatically before calling initialize():

flex.sigma_xx = 1e6   # east–west compression [Pa]
flex.sigma_yy = 0.
flex.sigma_xy = 0.

All three default to zero if not set. They are supported by fd and fft in 2-D, and by fd and fft in 1-D (sigma_xx only). Setting them with sas or sas_ng raises a warning and has no effect. See Theory and Numerics for the governing equations.

`numerical2D` section¶

grid_spacing_y: Grid cell size in the y-direction [m].
boundary_condition_north, boundary_condition_south: Same options as boundary_condition_west / boundary_condition_east.
latlon: true / false. Interpret input coordinates as geographic latitude and longitude. Default: false.
planetary_radius: Planetary radius [m]. Required when latlon = true. Earth: 6 371 000 m.

`verbosity` section¶

verbose: true / false. Print progress messages during the run. Default: true.
debug: true / false. Print internal arrays and solver diagnostics. Default: false.
quiet: true / false. Suppress all output. Overrides verbose and debug. Default: false.

Complete examples¶

1-D finite-difference example (YAML)¶

# All units are SI.

mode:
  dimension: 1
  method: fd

parameter:
  youngs_modulus: 6.5e10
  poissons_ratio: 0.25
  gravitational_acceleration: 9.8
  mantle_density: 3300
  infill_material_density: 0

input:
  loads: q0_sample/1D/central_block.txt
  elastic_thickness: Te_sample/1D/8km_20km_ramp.txt

output:
  deflection_out: ""
  plot: combo          # overlay deflection and load (1-D only)

numerical:
  grid_spacing_x: 6000
  boundary_condition_west: periodic
  boundary_condition_east: periodic

verbosity:
  verbose: false
  debug: false
  quiet: false

2-D finite-difference example (YAML)¶

# All units are SI.

mode:
  dimension: 2
  method: fd

parameter:
  youngs_modulus: 6.5e10
  poissons_ratio: 0.25
  gravitational_acceleration: 9.8
  mantle_density: 3300
  infill_material_density: 0

input:
  loads: q0_sample/2D/diag.txt
  elastic_thickness: Te_sample/2D/fault_24-30.txt

output:
  deflection_out: ""
  plot: both

numerical:
  grid_spacing_x: 4000
  boundary_condition_west: zero_moment_zero_shear
  boundary_condition_east: zero_displacement_zero_slope

numerical2D:
  grid_spacing_y: 4000
  boundary_condition_north: zero_slope_zero_shear
  boundary_condition_south: zero_slope_zero_shear

verbosity:
  verbose: false
  debug: false
  quiet: false

Configuration Files¶

Parameters¶

mode section¶

parameter section¶

input section¶

output section¶

numerical section¶

numerical2D section¶

verbosity section¶

Complete examples¶

1-D finite-difference example (YAML)¶

2-D finite-difference example (YAML)¶

`mode` section¶

`parameter` section¶

`input` section¶

`output` section¶

`numerical` section¶

`numerical2D` section¶

`verbosity` section¶