Ramified Deformable Particles in Simple Shear

Abstract The behavior of deformable structures in fluid flows is a standard problem, but normally involves the interaction between a complex flow and a complex structure. Fibers are an example such an interaction: the curvature of a fiber in a fluid flow will correspond to the derivative of the velocity gradient tensor. In simpler flows however, where the velocity gradient tensor remains constant over time, fibers exhibit no deformation, making them no more useful than non-deformable structures. [1] We have identified a new opportunity for deformable structures by using deformable ramified particles. These particles interactions with linear velocity fields (i.e. flows with constant velocity gradient tensors) are simple enough that we can extract the full velocity gradient from a single deformable particle. Normally, numerous non-deformable particles would be required to extract the same information. This is of particular value when studying turbulent flows. Turbulent flows exhibit linear behavior at the kolmogorov length, but because this length is often exceedingly small, the seed density (density of tracer particles) needed to re-assemble the full velocity gradient tensor is prohibitively high. Using deformable ramified particles, which extract far more information on a per particle basis, we can make the same measurements while maintaining a low seed density. The use of ramified deformable particles represents a novel development in the field of fluid dynamics. As a proof of concept, we set out to test them in a simple, well understood fluid flow with well known fluid structure interactions.