Fluid Dynamics / D2Q9 LBM

Navier-Stokes Flow Studio

This real-time fluid playground uses a D2Q9 lattice Boltzmann scheme with BGK relaxation for the momentum field and semi-Lagrangian dye advection for the visible tracer. The renderer now layers bloom, curl-based shading, and specular highlights so the flow reads like a denser, more textured fluid instead of a flat heatmap.

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Live State

FPS 0

Peak Speed 0.000

Dye Energy 0.000

Grid 160 x 160

Presets

Flow Looks

Presets adjust the simulation and rendering controls together, so the fluid appearance changes with the underlying flow instead of only recoloring the same field.

Simulation

Core Controls

Grid Resolution 160 x 160 Higher resolutions capture finer vortices but cost more per frame.

Viscosity via Tau tau = 0.95 In the BGK model, larger tau means more viscosity and softer, more diffused flow.

Dye Dissipation 0.04 Controls how quickly the visible tracer fades after it has been advected through the field.

Flow Exaggeration x1.40 Amplifies the dye advection visually without changing the underlying momentum update.

Force Strength 1800 Sets the impulse transferred into the fluid when you drag or when emitters inject momentum.

Brush Size 24 px Used for both dye injection and obstacle painting.

Emitter Rate 40 / s Approximate number of splats emitted per second by each continuous source.

Emitter Radius 18 px Controls the spatial spread of the continuous emitters. This now directly drives the emitter plume width.

Rendering

Visual Finish

Color Mode

Dye Color

Background

Bloom Strength 0.70 Adds a blurred screen-space glow pass on top of the crisp fluid field.

Texture Depth 0.75 Increases curl shading, interior highlights, and local variation derived from the velocity field.

Wrap Boundaries

Show Velocity Vectors

Obstacle Painting

Continuous Emitters

Readout

Field Summary

LBM State D2Q9 / BGK

Active Preset Smooth Ink

Emitters 2 active

Density Bounds 0.20 to 4.00

Method

What Is Being Simulated

The momentum field evolves through collision and streaming on a D2Q9 lattice, which is a standard lattice Boltzmann approximation for incompressible flow. The visible dye is not fed back into the fluid solve; it is advected separately as a tracer so you can see vortices, jets, and shear layers clearly in real time.

Momentum: BGK relaxation drives each cell toward its local equilibrium distribution after external forcing is applied.

Advection: dye uses a semi-Lagrangian backtrace, which is stable for interactive use and avoids exploding when the user injects strong impulses.

Rendering: the fluid image now blends low-resolution dye, curl-based shading, bloom, and highlight passes so the final result has more internal structure and depth.