Iron Rain Column: Stokes Settling & Core Growth (2D)

This 2D companion to the 3D planetary-differentiation sim recreates the same molten-iron "rain" as a vertical sedimentation column instead of a full sphere — the standard way settling experiments are actually visualized. Rather than assuming each droplet is already moving at its Stokes terminal velocity, every droplet's velocity is integrated from the real force balance (gravity and buoyancy against viscous drag), using an exact exponential solution because the underlying relaxation is numerically stiff at these droplet sizes. The result converges to the identical terminal-velocity formula the 3D sim uses, but arrives there through genuine dynamics — and the panel surfaces two diagnostics the 3D sim never computes: the relaxation time constant itself, and a live Reynolds number that flags exactly when the slider settings have pushed the system outside Stokes' law's valid regime. Tune grain size, mantle viscosity and gravity to watch the core layer grow from real conservation of settled volume.