Identical physical model to the 3D simulator, reproduced exactly (verified numerically in a standalone Node scratch script, never shipped — for d = 1, 15, 50, 100 μm the settling velocities came out 0.028, 6.225, 69.164, 276.655 mm/s, and the 100 μm / 15 μm ratio was 44.4×, matching the 3D sim's own "~45× faster" claim to within rounding — so no correction was needed, the formula checks out):
v_s = (ρ_p − ρ_air) · g · d² / (18 · μ_air)
ρ_p ≈ 920 kg/m³ ρ_air ≈ 1.2 kg/m³
μ_air ≈ 1.81×10⁻⁵ Pa·s g = 9.81 m/s²
x += (U + turbulent_u) · dt (downwind)
y += (turbulent_v − v_s) · dt (height, y=0 is ground)
What's genuinely different is the view: the 3D sim renders a perspective scene you orbit with the mouse; this 2D companion draws the exact same side-profile — downwind distance on the x-axis, height on the y-axis — as a flat, pannable, zoomable plot, plus a small settling-velocity-vs-diameter reference curve so you can see at a glance where the current diameter slider sits on the d² curve, not just its single readout value.
- Wind speed — mean horizontal transport; higher wind stretches the plume and pushes deposition further downwind.
- Particle diameter — sets vs via the d² term; small fibers stay airborne and disperse, large fragments settle almost immediately near the source.
- Turbulence intensity — random-walk strength that spreads the plume vertically, competing against steady settling.
- Emission rate — new fibers released per second from the source stack.
- This size-dependent settling is exactly why fine microplastic fibers are found in atmospheric deposition far from any obvious source, including remote mountains and polar ice.