Sophisticated numerical simulations reveal that the sponge's beautiful structure, known as the Venus flytrap, reduces hydrodynamic drag and likely helps capture food particles and sperm for sexual reproduction. The sponge Euplectella aspergillum, also known as the Venus flytrap, is famous for its intricate glassy skeleton. This structure provides exceptional mechanical support and has inspired the construction of lightweight bridges and skyscrapers. Water is constantly drawn in and out of the sponge's central body cavity through pores to filter food particles and exchange gases. Although the mechanical properties of the sponge skeleton are well documented, little is known about the detailed fluid flows around and through the body. The skeleton consists of a regular square lattice that is diagonally reinforced and forms a framework for the sponge's hollow cylindrical body. To deconstruct the effect of each skeletal component on fluid flow, Falcucci and colleagues created several idealized models of the sponge for comparison. These designs included a plain solid cylinder, a solid cylinder with spiral ridges, a hollow cylindrical grating, and a hollow cylindrical grating with spiral ridges.

Determining the fluid flow for these different models required extremely precise fluid dynamics simulations. These can simultaneously resolve levels of detail ranging from microscopic flows around the skeleton to massive flows around the entire organism. To make these experiments feasible, Falcucci et al. numerically solved the equations governing such flows using a method that is particularly well-suited to parallel computing on electronic circuits, called graphics processing units. In addition, the authors ran the simulations on Marconi100, one of the world's most powerful supercomputers.

This work represents an outstanding example of how state-of-the-art numerical simulations can be used to explore problems in fields such as biomechanics, fundamental fluid dynamics, and bioinspired design. Falcucci and colleagues' results show that many of the complex structures observed in marine invertebrates and other organisms have counterintuitive implications for fluid dynamics. The authors' approach could be applied to a number of puzzles in nature, related not only to food filtration, gas exchange, and drag reduction, but also to pollen capture and heat loss. Such multiscale flow simulations could, for example, be used to understand the hydrodynamics of gas exchange through coral reefs or the aerodynamics of pollen capture.

Furthermore, this study of the Venus flytrap reveals how complex geometries can manipulate fluid flow for multiple functions, including drag reduction, mechanical support, and particle filtration. Lessons learned from this organism could inspire improved multifunctional engineering structures, such as sampling and filtration devices.

Contribution Nature.com

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