Motion of large non-spherical particles in 2D flow

Large non-spherical floating objects, such as logs, ice, and debris, are common in environmental flows. Their relatively large sizes and irregular shapes can cause them to exhibit complex responses to the underlying flow; however, it is not clear how the effects of both finite size and anisotropic shape together affect the behavior of these objects in the flow. Particle shape changes how finite-sized particles respond to velocity gradients, which can affect their transport and distribution. To investigate how size and shape affect how these objects sample the flow, we simulate inertialess non-spherical particles in a 2D flow, idealized as ellipses and rods. We find that, even in the inertialess limit, these particles display patterns of preferential concentration solely due to their geometry. For example, highly anisotropic objects tend to concentrate in regions of higher vorticity. We also find that object behavior can be categorized into distinct regimes; for example, in a cellular flow, we observe steady, periodic, and chaotic motion depending on object size and shape.