# 📐 L2 Spec — Fluid-Structure Interaction (FSI) — coupled fluid + solid Mismatch-Only Spec
**ID:** `L2-194-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-194`](/artifact/l1/L1-194)
> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.48 · **Delta tier:** 5
> **⛓ On-chain block:** 41553980
---
## 1. Domain Ω
**Type:** `range`
| Parameter | Unit | Range |
|---|---|---|
| Snr db | dB | 0 – 40 |
| N times | — | 100 – 1000000 |
| N fluid dof | — | 1000 – 10000000 |
| N solid dof | — | 100 – 1000000 |
| Added mass error | — | 0.0 – 0.5 |
| Mesh motion error | — | 0.0 – 0.3 |
| Solid damping error | — | 0.0 – 0.3 |
| Interface mapping error | — | 0.0 – 0.3 |
## 2. Tolerance (ε)
**Type:** `fn`
```
12.0 + 0.3*SNR_dB - 10.0*interface_mapping_error - 8.0*added_mass_error - 5.0*solid_damping_error - 10.0*mesh_motion_error
```
## 3. Difficulty
| Property | Value |
|---|---|
| Difficulty score | 0.48 |
| Delta tier | 5 |
## 4. Fingerprint
`897b6d5e40e84e5eb10121349711976dc971695363d3b75d20e97c167f428523`
## 5. On-chain Registration
- **Chain hash:** `0xf9b4571d103021342c162087a053ab07d3fc5ac009aea030ffc72c5f81cad220`
- **Chain tx hash:** `0x663171ca28bc19a0c1ef23725df136aa1cc72fed152c1e39804c2007fb723ec3`
- **Chain block:** `41553980`
---
## File Mapping
This bundle consists of: `L2-194-001.md`, `L2-194-001.json`.
| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-194-001.md` | Source of truth — edit this | Human or LLM |
| `L2-194-001.json` | Structured metadata for the registry | LLM regenerates from the sections above |
**Prompt for your LLM after editing this Markdown:**
> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.
_This Markdown was auto-synthesized from the catalog row for `L2-194-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._