Gridding Block¶

The Gridding Block specifies the mesh distribution for the simulation, controlling how grid density varies across the domain. It offers five grid-generation options, including a uniform grid, a center-refined grid, a boundary-refined grid, a hyperbolic-tangent-refined grid, and a fully custom grid, allowing users to tailor local resolution to key flow regions.

Warning

This block is mandatory for all simulations.

Flags Overview¶

Note

All flags and their description are included in the table below. A detailed description of which values are possible for each input flag follows.

Flag	Required	Description
`XGRID_TYPE`	Yes	grid type in \(x\) direciton.
`YGRID_TYPE`	Yes	grid type in \(y\) direciton.
`ZGRID_TYPE`	Yes	grid type in \(z\) direciton.
`TAU_STR_CENTER_X`	No	stretching ratio for a center-refined grid in x-direciton.
`TAU_STR_CENTER_Y`	No	stretching ratio for a center-refined grid in y-direciton.
`TAU_STR_CENTER_Z`	No	stretching ratio for a center-refined grid in z-direciton.
`REF_CENTER_X`	No	center of refinement [meter] in x-direciton.
`REF_CENTER_Y`	No	center of refinement [meter] in y-direciton.
`REF_CENTER_Z`	No	center of refinement [meter] in z-direciton.
`BETA_G_BOUND`	No	stretching ratio for a boundary-refined grid.
`VALS_TANH_x`	No	parameters for a hyperbolic-tangent-refined grid.
`VALS_TANH_y`	No	parameters for a hyperbolic-tangent-refined grid.
`VALS_TANH_z`	No	parameters for a hyperbolic-tangent-refined grid.

Flags Details¶

GRID_TYPE

Type: integer
Default: 1
Description: 1 represents a uniform grid, 2 represents a center-refined grid, 3 represents a boundary-refined grid, 4 represents a hyperbolic-tangent-refined grid, 5 represents a fully custom grid. Note: Use GRID_TYPE = 5 with caution, because if the Jacobian transformations (and its first or second derivatives) associated with the stretched mesh are not continuous, it may lead to numerical errors.

TAU_STR_CENTER

Type: real
Default:
Description: positive real variables. This variable is only used when GRID_TYPE=2.

REF_CENTER

Type: real
Default:
Description: nonnegative real variables. This variable is only used when GRID_TYPE=2.

BETA_G_BOUND

Type: real
Default:
Description: positive real variables. This variable is only used when GRID_TYPE=3.

VALS_TANH

Type: real
Default:
Description: groups of three parameters (ratio, tp, delta). This variable is only used when GRID_TYPE=4.
Each group defines one refinement region. ratio: refinement strength. Values > 1 locally compress the grid, while values < 1 stretch it. tp: the center position of the refinement region. delta: the stretching width; larger \(abs(delta)\) produces smoother, wider transitions.
For example, the full parameter set (40, 0.000150, -0.00001, 40, 0.007849, 0.00001, 0, 0, 0) corresponds to two active hyperbolic-tangent refinement zones. First refinement region: ratio=40, tp=0.00150, delta=-0.00001. Second refinement region: ratio=40, tp=0.007849, delta=0.00001. Last triplet: ratio=0, tp=0, delta=0, which is unused.

Example:¶

&NML_GRIDDING
    XGRID_TYPE=1,
    YGRID_TYPE=1,
    ZGRID_TYPE=1,
    TAU_STR_CENTER_X=2.d0,
    TAU_STR_CENTER_Y=2.d0,
    TAU_STR_CENTER_Z=2.d0,
    REF_CENTER_X=5.d-3,
    REF_CENTER_Y=6.d-3,
    REF_CENTER_Z=2.d0,
    BETA_G_BOUND=0.5d0,
    VALS_TANH_x = 28.0,0.00077,-0.0001,28.0,0.0094,0.0001,
    VALS_TANH_y = 24.0,0.00125,-0.0007,24.0,0.019,0.0005,
    VALS_TANH_z = 10,0.1,0.05,10,0.9,-0.05,
/