Fluid

Interactive 2D fluid simulator using a staggered-grid Eulerian solver with semi-Lagrangian advection and optional BFECC error correction.

Visualization

• S: Cycle visualization mode: Smoke → Pressure → Velocity Magnitude → Vorticity
• A: Toggle velocity arrow overlay
• P: Toggle particle tracer visibility
• H: Toggle help overlay

Simulation

• J: Toggle the jet inlet
• V: Toggle vorticity confinement
• B: Toggle BFECC advection (sharper, less diffusive)
• Space: Pause or resume the simulation
• +/-: Increase or decrease simulation speed
• R: Reset to the current preset

Tools

Select tools with keyboard, apply with left-click drag:

• W: Wall tool — draw solid walls
• E: Erase tool — remove walls
• F: Force tool — push fluid along drag direction
• K: Smoke tool — inject smoke (also spawns tracer particles)
• O: Source tool — place persistent velocity source
• N: Sink tool — place persistent velocity sink
• Tab: Cycle through tools

Brush

• [/]: Decrease/increase brush radius
• ,/.: Decrease/increase brush strength

Mouse

• Left-click drag: Apply the active tool
• Right-click drag: Always apply force impulse (regardless of active tool)

Walls

• Arrow keys Up, Down, Left, Right: Toggle the corresponding border wall
• C: Remove all walls except the active border walls

Presets

• 1: Jet flow (default)
• 2: Lid-driven cavity
• 3: Karman vortex street (flow past circular obstacle)