# wall kind free_space

Describes the entry `free_space` at version `0.1.0`, registered by `mime.walls.FreeSpaceWall`.

## At a glance

- wall kind `free_space`, version `0.1.0`, namespace `mime`
- Derivative: `exact`
- Validity: 1 declared line

## What it models, and when not to use it

### `free_space`

No wall: a medium that fills no region, unbounded, so a solver adds nothing to its free-space kernel. It is the
trivial analytic wall kind, and the one a body far from every wall is read in.

**When not to use it.** For a medium that fills a region (a tube's lumen): a wall left out changes the flow, so the
experiment is refused with it, naming the wall kinds that match the region.

**Versions.** The first, landed with the wall-kind interface; the free-space regularised-Stokeslet
method it replaced took the same setting.

## Settings

none: the entry takes no setting, so its `setting_roles` declares none.

## Nodes it builds

Builds no node of its own.

## Gradient status

The derivative through this entry is `exact`, the derivative of what it computes.

## Validity

Declared validity lines: free text, not parsed, and not yet checked against the operating point or the region each one describes.

- an unbounded medium: no wall within the reach of the body's flow

## References

none declared

## Other declarations

| Class variable | Type | Value |
|---|---|---|
| `form` | `ClassVar[WallForm]` | `analytic` |
| `matches` | `ClassVar[str \| None]` | `null` |
| `moving` | `ClassVar[bool]` | `false` |