---
title: Case schema
summary: Every field of the case specification with its type, default and, where the model carries one, a description — generated from the pydantic model that validates it. Fields whose description cell is empty are explained in the Cases guide.
section: reference
order: 1
level: 2
keywords: [schema, CaseSpec, reference]
---
<!-- gyre docs: expanded Markdown of reference/case-schema.md (generated tables, verification numbers and chart data are written out). Base level of this page: L2 Practice; passages at another level are bracketed by 'begin level N' / 'end level N' comments and start with [LN Name]. Built from revision ceb1f4b0be. -->

**CaseSpec** — Complete, serialisable description of a steady flow analysis.

| field | type | default | description |
|---|---|---|---|
| `name` | string | `case` | (max length 80, pattern ^[A-Za-z0-9_.-]+$) |
| `description` | string |  |  |
| `mesh` | MeshSpec | `*required*` |  |
| `flow` | FlowSpec |  |  |
| `discretization` | DiscretizationSpec |  |  |
| `solver` | SolverSpec |  |  |
| `reference` | ReferenceSpec |  |  |

**MeshSpec** — Built-in mesh generator and its parameters, or a mesh file (``generator: file``).

| field | type | default | description |
|---|---|---|---|
| `generator` | `airfoil_omesh` \| `annulus` \| `bump_channel` \| `flat_plate` \| `sphere_shell` \| `box` \| `file` | `*required*` | Name of the built-in mesh generator, or 'file' for an external mesh (params: path, optional scale; Gmsh .msh 2.2/4.1 ASCII or Gyre .npz). |
| `params` | mapping |  | Keyword arguments of the generator (e.g. n_surf, n_radial, r_far, code); unknown, missing or mistyped arguments are validation errors. |
| `geometry_order` | integer | `4` | Polynomial degree of the curved elements (generators only: a mesh file carries its own degree). (≥ 1, ≤ 8) |

**FlowSpec** — Free-stream / reference flow conditions (all differentiable inputs).

| field | type | default | description |
|---|---|---|---|
| `mach` | number | `0.5` | Free-stream Mach number. (> 0.0, < 5.0) |
| `alpha_deg` | number | `0.0` | Angle of attack in degrees. (≥ -90.0, ≤ 90.0) |
| `beta_deg` | number | `0.0` | Sideslip angle in degrees (3-D only; ignored in 2-D). Free-stream direction: (cos a cos b, sin a cos b, sin b). (≥ -90.0, ≤ 90.0) |
| `reynolds` | number or null | `None` | Reynolds number (unit reference length); null means inviscid. |
| `prandtl` | number | `0.72` | (> 0.0) |
| `gamma` | number | `1.4` | (> 1.0) |
| `turbulence` | `none` \| `sa` | `none` | Turbulence closure: 'none' (laminar or inviscid) or 'sa' (negative Spalart-Allmaras RANS model; requires reynolds). |
| `extra` | mapping |  | Additional boundary data: p_back, pt_in, tt_in, t_wall, suth; with turbulence 'sa' also chi_inf (free-stream nu_tilde/nu, default 3) and prt (turbulent Prandtl number, default 0.9). |

**DiscretizationSpec** — Spatial discretization.

| field | type | default | description |
|---|---|---|---|
| `order` | integer | `2` | Solution polynomial degree p (accuracy p+1); viscous cases need p >= 1. (≥ 0, ≤ 8) |
| `two_point_flux` | `ranocha` \| `chandrashekar` \| `kennedy_gruber` \| `central` | `ranocha` |  |
| `surface_flux` | `roe` \| `es_roe` \| `hllc` \| `llf` | `roe` | Interface flux: 'roe' and 'hllc' are the classical solvers; 'es_roe' (matrix dissipation in entropy variables) and 'llf' (scalar dissipation) are entropy stable with an entropy-conservative two_point_flux. |
| `shock_capturing` | boolean | `False` | Sensor-based artificial viscosity for flows with shocks. |
| `av_coef` | number | `1.0` | Artificial-viscosity scale (multiples of h/p * (\|u\|+c)). (> 0.0, ≤ 10.0) |
| `boundaries` | mapping |  | Boundary group -> condition; defaults are chosen per generator. |

**SolverSpec** — Nonlinear and linear solver controls.

| field | type | default | description |
|---|---|---|---|
| `levels` | list of integer or `auto` \| `single` | `auto` | p-multigrid degrees fine->coarse, 'auto' (p, p//2, ..., 0) or 'single'. |
| `tol_rel` | number | `1e-10` | (> 0.0, < 1.0) |
| `max_steps` | integer | `150` | (≥ 1, ≤ 5000) |
| `cfl0` | number | `5.0` | (> 0.0) |
| `cfl_growth` | number | `10.0` | (≥ 1.0) |
| `cfl_shrink` | number | `1.0` | Factor applied to the CFL number after a step that the line search shortened to a quarter or less (1: hold the CFL). (> 0.0, ≤ 1.0) |
| `lin_tol` | number | `0.01` | (> 0.0, < 1.0) |
| `krylov_dim` | integer | `40` | (≥ 5, ≤ 400) |
| `restarts` | integer | `2` | (≥ 1, ≤ 50) |
| `smoother` | `jacobi` \| `gmres` \| `line` | `jacobi` | Smoother of the p-multigrid levels: damped block Jacobi, block-Jacobi GMRES, or line Jacobi (block-tridiagonal solves along lines of strongly coupled elements of an anisotropic mesh; block Jacobi where the mesh has none). |
| `precond_lag` | integer | `1` | Assemble the blocks of the smoother every this many nonlinear steps (1: every step). In between, the last blocks are reused. (≥ 1, ≤ 50) |
| `precond_precision` | `double` \| `single` | `double` | Precision in which the blocks of the smoother are assembled, stored and applied. 'single' halves their memory, which is what bounds the size of a 3-D problem on one device; the residual, its Jacobian products, the Krylov vectors and the inverses stay in double precision, so the solution is unchanged and only the iteration count can differ. |

**ReferenceSpec** — Reference quantities of the force and moment coefficients.

| field | type | default | description |
|---|---|---|---|
| `area` | number or null | `None` | Reference area (length in 2-D). Default: 1 in 2-D, the span of a spanwise-extruded generator mesh in 3-D, the frontal area of the body of a sphere_shell mesh. |
| `length` | number | `1.0` | Reference length of the moment coefficient. (> 0.0) |
| `moment_center` | list of number |  | Point about which the moment is taken. |
| `groups` | list of string or null | `None` | Wall boundary groups over which the force, moment and heat-flux coefficients are integrated (the loads of one component). Default: every wall group of the mesh. The nodal load field f_surface and the surface displacement x_surface always cover all walls. |
| `components` | mapping or null | `None` | Named components of the walls, each a list of wall boundary groups. Every force, moment and heat-flux coefficient is then also an output per component, named <coefficient>_<component> (cd_wing, cl_tail, ...), from the same solve and with its own derivatives. Names are letters and digits. |

The table is generated from the model, so a field has a description here only if the model
declares one. The meaning of the remaining fields — the flux choices, the solver controls,
`flow.prandtl`, `flow.gamma` and the keys of `flow.extra` — is given under
[Cases](../guide/cases.md), and the generator parameters under
[Mesh generators](../guide/cases.md#anatomy-of-a-specification).

## Presets

| preset | description | elements | DOF | model |
|---|---|---|---|---|
| `naca0012_euler` | Inviscid subsonic flow over a NACA 0012 aerofoil (M=0.5, alpha=2 deg). | 256 | 9,216 | Euler, 2-D |
| `naca0012_laminar` | Laminar flow over a NACA 0012 aerofoil (M=0.5, alpha=1 deg, Re=5000). | 480 | 17,280 | Navier–Stokes, 2-D |
| `naca2412_euler` | Inviscid flow over a cambered NACA 2412 aerofoil (M=0.4, alpha=1 deg). | 256 | 9,216 | Euler, 2-D |
| `naca0012_transonic` | Transonic inviscid flow over a NACA 0012 aerofoil (M=0.8, alpha=1.25 deg) with sensor-based shock capturing. | 1024 | 36,864 | Euler, 2-D |
| `naca0012_euler_3d` | Spanwise-periodic 3-D extrusion of the inviscid NACA 0012 case (hexahedra): exercises the 3-D operators, solver and adjoint; coefficients per unit span. | 192 | 25,920 | Euler, 3-D |
| `cylinder_re40` | Steady separated laminar flow past a circular cylinder (Re_D=40, M=0.2). | 240 | 15,360 | Navier–Stokes, 2-D |
| `sphere_euler` | Inviscid subsonic flow past a sphere (M=0.2) on a cubed-sphere mesh of curved hexahedra: a genuinely 3-D, unstructured-topology case whose exact solution has no drag and no entropy rise. | 216 | 29,160 | Euler, 3-D |
| `sphere_re100` | Steady laminar flow past a sphere (Re_D=100, M=0.2): 3-D Navier-Stokes with a closed recirculation bubble; drag referred to the frontal area. | 576 | 77,760 | Navier–Stokes, 3-D |
| `flat_plate_sa` | Turbulent flat plate at zero pressure gradient (M=0.2, Re=5e6 per unit length) with the Spalart-Allmaras model: the NASA Turbulence Modeling Resource verification case on a coarse wall-resolved mesh. | 150 | 6,750 | Navier–Stokes, 2-D |
| `bump_euler` | Inviscid subsonic channel flow over a smooth Gaussian bump (M=0.5): the exact solution is isentropic, so the entropy error measures accuracy. | 48 | 3,072 | Euler, 2-D |