Fluid dynamics simulator

Three ways to see a fluid move. Potential-flow streamlines show how air divides around an obstacle and where pressure builds, a vortex method sheds a Kármán street behind a cylinder, and smoothed-particle hydrodynamics collapses a column of water across a tank.

This interactive simulation runs in your browser with WebGL. Free, no account needed.

What you can explore

Streamlines

Flow around an obstacle, coloured by the pressure coefficient. Streamlines crowd together where the fluid speeds up and pressure drops, as Bernoulli’s principle predicts.

Vortex shedding

Behind a cylinder, vortices peel off alternately from each side and form a Kármán vortex street. Raise the Reynolds number and the shedding grows stronger.

SPH dam break

A column of water modelled as hundreds of particles collapses, surges across the tank and splashes back, computed with smoothed-particle hydrodynamics.

Key equations

  • ρ(∂u/∂t + u·∇u) = −∇p + μ∇²u
  • Re = ρvL / μ
  • p + ½ρv² = constant

Curriculum

Enrichment: fluid mechanics.

Common questions

What is the Reynolds number?

The ratio of inertial to viscous forces in a flow. Low values give smooth, laminar flow; high values lead to vortex shedding and eventually turbulence.

Why do vortices shed alternately?

Once the wake behind an obstacle becomes unstable, a vortex forming on one side changes the flow on the other, so they peel off in turn and create a regular, alternating pattern.

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