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Torques on curved atmospheric fibers
Summary
This physics study derived a mathematical model describing how curved fibers — such as curved microplastic fibers or ash particles — rotate and orient themselves as they settle through still air. Unlike symmetric particles, curved fibers experience fluid-inertia torques that tilt them at oblique angles, affecting how far they travel and where they deposit. The work is relevant to understanding airborne microplastic fiber transport: curved fibers behave differently from straight ones or spherical particles, and accurate transport models are needed to predict their deposition patterns.
Small particles are transported over long distances in the atmosphere, with significant environmental impact. The transport of symmetric particles is well understood, but atmospheric particles, such as curved microplastic fibers or ash particles, are generally asymmetric. This makes the description of their transport properties uncertain. Here, we derive a model of how planar curved fibers settle in quiescent air. The model explains that fluid-inertia torques may align such fibers at oblique angles with gravity as seen in recent laboratory experiments, and shows that inertial alignment is a general and thus important factor for the transport of atmospheric particles.
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