A Boundary Integral Approach to Breaking Up Marine Aggregates

Near the surface of the ocean, particulates and other microorganisms tend to cluster and form fractal aggregates as they meet. The mechanisms that lead to their formation have been studied extensively. It is also well known, but not well understood, that marine aggregates often break up as they settle under gravity, or because of stresses induced by some background flow. Here we propose a Boundary-Integral formulation of the Stokes Equations that allows us to compute the internal stresses felt by fractal aggregates subjected to different background flows. When the maximum internal stress computed exceeds a pre-defined threshold, aggregates are broken up in two. For aggregates with various fractal dimensions, we study the relationship between the stresses and the size of the original objects and quantify the fractal dimensions of the newly formed objects. This study provides a more realistic description of aggregates observed in experiments, and gives insight on how to build more accurate disaggregation models.