Torques on curved atmospheric fibers

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.