Fluid–structure interactions (FSI) are ubiquitous in many natural and man-made environments. They are difficult to study analytically, and therefore accurate and flexible computational methods are an indispensable tool in the field. Typically, fluids are simulated with a fixed background computational mesh, whereas a solid is simulated with a mesh that moves with it, making it challenging to couple the two. Here we develop a computational method, called the reference map technique (RMT), where both fluid and solid can be represented on a fixed computational grid, which simplifies the coupling between the two phases considerably. The mathematical formulation of the RMT helps resolve nonlinear deformations in the solid structure. Three-dimensional FSI simulations with many solid bodies are rendered feasible and practical with our scalable, parallelized implementations. We demonstrate the RMT by simulating a broad category in FSI, a system with soft, immersed rods (spherocylinders). A rod provides a good geometric model for many immersed structures, ranging from microswimmers, to DNA molecules, to underwater cables. We investigate the body geometry of a rod as it settles under gravity, and demonstrate scenarios that are difficult to do with other methods, e.g. complex suspensions containing solids that are both heavier and lighter than the fluid.
Music in this video:
“The Ocean in a Drop” is created by Gotama; copyright is retained by the artist. The material is downloaded from the Free Music Archive (https://freemusicarchive.org/music/gotama/moving-silence/the-ocean-in-a-drop) under the license CC BY-NC 4.0 (https://creativecommons.org/licenses/by-nc/4.0/). The track has been shortened.