The flow of fluids through and past bodies containing fine-grained patterns of void, which makes them partially permeable to the flow itself, is of great interest both in nature and in engineering applications. Examples may include filtration problems, cooling systems or in general devices requiring wide exchanging surfaces. From an aerodynamic viewpoint porous bodies are less intrusive than the solid counterparts. This characteristic has been used as an advantage in nature in several examples which inspire equivalent engineering applications. One spectacular example is given for instance by the seeds of the Tragopon pratensis, which are transported by the wind thanks to a particular umbrella-like extensions called pappus, which can be seen as the equivalent of a parachute. This particular seed has been studied at DICI, in collaboration with EPFL (Lausanne), suggesting that the number of filaments in the pappus of Tragopon pratensis grants the stability of the resulting wake so as to make the seed flight stable while granting a sufficient drag, thus promoting wind dispersion.
The research activity carried out at DICI is focused on both modeling the porous medium and on exploring the physical characteristics of paradigmatic flow configurations when porous bodies are involved, with a specific interest for bluff bodies and for configurations suggested by nature, connecting the micro-scale voids pattern in the porous medium with the macroscopic aerodynamic characteristics of the corresponding porous bodies.
- Ledda, P. G., Siconolfi, L., Viola, F., Gallaire, F., & Camarri, S. (2018). Suppression of von Kármán vortex streets past porous rectangular cylinders. Physical Review Fluids, 3(10), 1–22.
- Ledda, P. G., Siconolfi, L., Viola, F., Camarri, S., & Gallaire, F. (2019). Flow dynamics of a dandelion pappus: A linear stability approach. Physical Review Fluids, 4(7), 071901.