Ocean Cleanup Boom: Windage & Debris Capture

Boom & Current

Tow speed 0.60 m/s

Boom mouth span 90 m

Mesh gap (min captured size) 15 mm

Wind / windage strength 0.40

Live Readouts

Capture efficiency

Captured

Slipped under mesh

Free-drifting debris Herded along boom Captured at net Below mesh gap (passes under)

How it works

A passive cleanup boom does not chase debris — it is towed slightly faster than the surface drift of the plastic it targets, so it continuously overtakes debris ahead of it. The relative (boom-frame) velocity of a debris particle is:

v_rel = (v_current + v_windage) − v_tow
v_windage = k(size) · W        (wind-driven "sail" effect above the waterline)

Larger objects (bottles, nets, crates) sit higher out of the water and pick up a bigger windage coefficient k(size); tiny microplastic fragments are almost fully submerged and drift with the current alone. Because v_tow > v_current for the design range, most debris has v_rel pointing into the boom's mouth — it appears to drift backward relative to the barrier and is herded along the two arms toward the retention zone at the apex, exactly as The Ocean Cleanup's System 002/003 U-shaped booms work in open water.

The funnel's half-width narrows linearly from the mouth to the apex:

halfWidth(x) = (span/2) · (1 + x/armLength),   x ∈ [−armLength, 0]

Two things let debris escape even inside the funnel:

Mesh gap — any particle smaller than the mesh-gap threshold slips straight underneath the boom's skirt instead of being herded, exactly like real microplastics passing under a surface barrier.
Windage outrunning tow speed — push wind strength high enough on large, high-windage debris and its own drift can exceed the boom's tow speed, letting it outrun and escape the mouth before being funneled in.

Capture efficiency here is captured ÷ (captured + missed), counted only among particles that actually entered the funnel — a direct analogue of the retention-rate metric used to evaluate real ocean-cleanup deployments.

Tow direction → 0 captured/min

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