Fluid Simulation Screensaver
The Fluid Simulation screensaver runs a real live fluid dynamics simulation, advecting colored dye through a swirling velocity field. It is free, runs in your browser, and ESC exits.
Live preview
Press ESC to leave fullscreen. Settings are saved in your browser only.
How the Fluid Simulation screensaver works
The saver simulates a real velocity field using a simplified Navier-Stokes-inspired advection and diffusion method.
Colored dye is injected periodically and carried along by the simulated flow.
Swirling vortices form naturally from the underlying fluid math, just like real smoke or ink in water.
The simulation runs continuously, so the flow keeps evolving and never settles.
Simulating fluids on a computer
The motion of liquids and gases is described by the Navier-Stokes equations, written down in the nineteenth century. They link a fluid’s velocity to pressure, viscosity and external forces. Whether solutions always exist in three dimensions, and stay well behaved, is an unsolved question that the Clay Mathematics Institute lists among its Millennium Prize problems. Computers sidestep it by approximating the equations step by step on a grid.
A landmark for real-time graphics was Jos Stam’s 1999 SIGGRAPH paper Stable Fluids. Its key trick, called semi-Lagrangian advection, finds where a patch of fluid on the grid came from by tracing the velocity field backwards, and copies the value from there. The method is unconditionally stable, so large time steps do not make the simulation blow up, which is why it became a standard basis for interactive smoke and ink effects.
Dye is a passive marker: it is carried along by the flow without changing it, which makes the invisible velocity field visible. Real engineering simulation software uses much finer and more elaborate methods; a screensaver version aims at looking convincing rather than predicting real forces.
A worked example
A fresh burst of dye is swept immediately into a forming vortex, stretching into a long spiral streak as the flow curls around it.
Settings & tips
- Accent tints the dye color.
- Based on the real fluid-dynamics methods used in visual effects software.
- The flow never fully settles — it keeps evolving.
Frequently asked questions
- Is this based on real fluid dynamics?
- Yes — a simplified Navier-Stokes-inspired advection and diffusion simulation.
- Is a key needed?
- No — it is a pure local simulation.
- Is it free?
- Yes — free, no download, in your browser.
- Does the flow ever repeat?
- No — small variations compound over time, so it never repeats exactly.
- What are the Navier-Stokes equations?
- They are the equations that describe how a fluid’s velocity changes with pressure, viscosity and external forces, and they underlie much of fluid mechanics.
- What is Stable Fluids?
- A 1999 SIGGRAPH paper by Jos Stam describing a fluid solver that stays stable even with large time steps, which made real-time smoke and liquid effects practical.
- What does the dye do?
- It is a passive marker carried along by the flow, so it shows the motion without affecting it.