Virtual MEchanics GAthering -MEGA- Seminar: Homogenization-based design of microstructured membranes: wake flows past permeable shells
Event details
| Date | 25.03.2021 |
| Hour | 16:15 › 17:30 |
| Speaker | Pier Giuseppe Ledda (LFMI, EPFL) |
| Location |
https://epfl.zoom.us/s/84678428267 Passcode: 174387
Online
|
| Category | Conferences - Seminars |
Abstract All of us have seen, at least once, flying dandelion fluffs transported by the wind. The flow around permeable obstacles is gaining more and more interest owing to its large range of applications. Here, a formal framework to characterize and optimize the flow past permeable membranes by means of a homogenization approach is proposed and applied to the wake flow past a permeable cylindrical shell.
An effective stress jump condition is employed to model the presence of the membrane, stating that the normal and tangential velocities at the membrane are respectively proportional to the so-called filtrability and slip numbers. The characterization of the steady flow solution for several filtrability and slip numbers, kept constant over the membrane, shows that the flow morphology is dominantly influenced by filtrability and exhibits a recirculation region that moves downstream of the body and eventually disappears as this number increases.
A linear stability analysis shows the suppression of vortex shedding as long as large values of the filtrability number are employed. A procedure to obtain the microscopic geometry based on macroscopic objectives is implemented and verified in case of constant values of filtrability and slip over the membrane. Variations of the filtrability and slip profiles along the membrane are then taken into account and those profiles are optimized to fulfill a given objective deduced from the flow features in the context of adjoint-based optimization. Fast-varying microscopic geometries are finally linked to the optimal profiles via a homogenization-based inverse procedure.
Bio PG Ledda is a Ph.D. student at the Laboratory of Fluid Mechanics and Instabilities at the EPFL. He obtained his B.sc and M.sc in Aerospace and Aeronautical Engineering at the University of Pisa. He joined EPFL during his master thesis, focused on the pattern characterization when a porous bluff body is invested by an asymptotic flow. He is now focused on the pattern formation in karst environments and the flow modelization using lubrication models. His main interests involve the flow control of aerodynamic flows by porosity variations and of thin films by textured substrates.
An effective stress jump condition is employed to model the presence of the membrane, stating that the normal and tangential velocities at the membrane are respectively proportional to the so-called filtrability and slip numbers. The characterization of the steady flow solution for several filtrability and slip numbers, kept constant over the membrane, shows that the flow morphology is dominantly influenced by filtrability and exhibits a recirculation region that moves downstream of the body and eventually disappears as this number increases.
A linear stability analysis shows the suppression of vortex shedding as long as large values of the filtrability number are employed. A procedure to obtain the microscopic geometry based on macroscopic objectives is implemented and verified in case of constant values of filtrability and slip over the membrane. Variations of the filtrability and slip profiles along the membrane are then taken into account and those profiles are optimized to fulfill a given objective deduced from the flow features in the context of adjoint-based optimization. Fast-varying microscopic geometries are finally linked to the optimal profiles via a homogenization-based inverse procedure.
Bio PG Ledda is a Ph.D. student at the Laboratory of Fluid Mechanics and Instabilities at the EPFL. He obtained his B.sc and M.sc in Aerospace and Aeronautical Engineering at the University of Pisa. He joined EPFL during his master thesis, focused on the pattern characterization when a porous bluff body is invested by an asymptotic flow. He is now focused on the pattern formation in karst environments and the flow modelization using lubrication models. His main interests involve the flow control of aerodynamic flows by porosity variations and of thin films by textured substrates.
Practical information
- General public
- Free
Organizer
- MEGA.Seminar Organizing Committee