Whirlpools usually fling heavy stuff away, but these 'dumbbell' shaped particles actually get sucked right into the middle and trapped.
arXiv · March 17, 2026 · 2603.14390
The Takeaway
Standard physics (and every kitchen blender) suggests that centrifugal force should expel heavy particles from the center of a vortex. However, researchers found that if a particle is long enough to feel two different parts of the spinning fluid at once, it can 'sample' the flow in a way that overcomes the centrifugal force, forcing it to spiral inward and stay trapped in the eye of the storm.
From the abstract
Most analyses of inertial particle motion in vortical flows rely on the point-particle approximation, in which the fluid velocity is assumed to be linear at the scale of the particle, and for heavy particles inertia typically leads to centrifugal expulsion from vortex cores. Here, we show that a spatially extended particle, modeled as a rigid symmetric dumbbell of two identical inertial point particles connected by a massless rod that samples the flow at two points, can converge to a vortex-cent