> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nomn.jp/llms.txt
> Use this file to discover all available pages before exploring further.

# Fluid Dynamics & Acoustics

> Liquid medium and physical resonance

These controls define the **liquid your bubbles exist within** and the **physical space they resonate inside**. Together they shape the fundamental tonal character of FOAM.

## Material Presets

The **Material** dropdown provides scientifically-accurate liquid presets. Each one sets density, surface tension, and viscosity to real measured values.

| Material          | Character                                     |
| ----------------- | --------------------------------------------- |
| **Custom**        | Manual control of all three liquid parameters |
| **Water**         | Bright, crisp pops — the reference liquid     |
| **Seawater**      | Slightly denser, the default starting point   |
| **Soap Solution** | Lower surface tension, longer-lived bubbles   |
| **Glycerol**      | Thick, gloopy, slow decay                     |
| **Honey**         | Very viscous, muted and heavy                 |
| **Olive Oil**     | Medium viscosity, organic warmth              |
| **Mercury**       | Extreme density, unusual resonance            |
| **Ethanol**       | Light, low surface tension                    |
| **Molasses**      | Most viscous, almost percussive thuds         |

## Manual Liquid Controls

When Material is set to "Custom" you have direct control. (These knobs are visible in all modes; selecting a preset overwrites them.)

| Knob            | What It Does                                                                                                                                   |
| --------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
| **Liquid Mass** | Density of the liquid (600-14000 kg/m³). Higher density = slightly lower pitch and different damping character.                                |
| **Tension**     | Surface tension (0.02-0.5 N/m) affects how bubbles form and burst. Low tension = fragile, quick pops. High tension = more crystalline ring.    |
| **Viscosity**   | How "thick" the liquid is (0.0003-12 Pa·s). Low viscosity (water) gives quick, bright decay. High viscosity (honey) gives slow, muffled decay. |

## Resonator

The **Resonator** dropdown applies a physical-space body resonance to all bubbles passing through it — as if the entire foam were happening inside a glass jar, a metal pipe, a cave, or your skull. Each preset is a multi-mode bandpass filter modeled on the real physics of that space.

| Preset           | Character                                                                     |
| ---------------- | ----------------------------------------------------------------------------- |
| **None**         | Bypass — no resonance applied                                                 |
| **Glass Jar**    | Bright, ringing — Helmholtz fundamental + cylindrical cavity modes (\~280 Hz) |
| **Metal Pipe**   | Perfectly harmonic, medium decay — open-open tube (\~170 Hz)                  |
| **Ceramic Bowl** | Inharmonic shell modes, warm and rounded (\~520 Hz)                           |
| **Bathtub**      | Dense, boomy — rectangular room modes (\~113 Hz)                              |
| **Underwater**   | Deep, muffled — water column resonance, heavy damping (\~65 Hz)               |
| **Seashell**     | Airy, whispery — Helmholtz + spiral cavity (\~380 Hz)                         |
| **Metal Bucket** | Harsh, clangy — high-Q metal shell (\~210 Hz)                                 |
| **Cave**         | Massive, infrasonic — large irregular room with very long decay (\~17 Hz)     |
| **Cistern**      | Extremely long decay, like Fort Worden — tall stone cylinder (\~28 Hz)        |
| **Well**         | Quarter-wave tube, odd harmonics dominant (\~8.5 Hz)                          |
| **Skull**        | Formant-like resonances modeled on bone conduction (\~200 Hz)                 |

| Knob          | What It Does                                                                               |
| ------------- | ------------------------------------------------------------------------------------------ |
| **Resonance** | Wet/dry mix amount (0-100%). At 0% the resonator is bypassed even if a preset is selected. |

<Tip>
  In Melodic and Harmonic Flow Types, the resonator's pitch tracks the lowest active MIDI note — turning the body resonance into a tunable instrument rather than a fixed character.
</Tip>

<Info>
  The Resonance amount knob is included in Chaos modulation, so right-click to lock it if you want a stable resonance while everything else moves.
</Info>