SPH dam break simulation
Smoothed-particle hydrodynamics (SPH) models a fluid as a crowd of particles that push on their neighbours. It handles splashes, waves and free surfaces naturally, which is why it is used for everything from film effects to tsunami modelling.
Interactive, free and runs in your browser. Part of the Fluid Dynamics simulations.
What you will see
A tall column of water collapses under gravity, surges across the tank, hits the far wall and splashes back before settling. Each particle is coloured by speed, from slow blue to white at peak impact.
Try this
- Watch the front of the surge: it moves fastest just after release.
- Look for the splash when the water hits the far wall.
- Wait for the water to settle and check the surface ends up level.
Common misconception
The particles are not water molecules. Each represents a small blob of fluid, and its density and pressure are smoothed over its neighbours rather than calculated molecule by molecule.
Exam-style question
In SPH, how is the density at a particle calculated?
As a weighted sum of the masses of nearby particles: ρᵢ = Σ mⱼ W(rᵢ − rⱼ, h), where W is a smoothing kernel that falls to zero beyond the smoothing length h. Pressure then follows from the density.
Key equations
ρᵢ = Σ mⱼ W(rᵢ − rⱼ, h)ρ(∂u/∂t + u·∇u) = −∇p + μ∇²u + ρg
Curriculum
Enrichment: fluid mechanics.