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SUMMARY:Interactions of Fluid Flows and Porous Structures
DTSTART:20180927T161500
DTEND:20180927T173000
DTSTAMP:20260510T202503Z
UID:6506f483fcc3b1001bf4b9f89defd565296026658d7b70d5d378eeac
CATEGORIES:Conferences - Seminars
DESCRIPTION:Pier Giuseppe Ledda\, EPFL STI IGM Laboratory of Fluid Mechani
 cs and Instabilities (LFMI)\; Matteo Pezzulla\, EPFL STI IGM  Flexible S
 tructures Laboratory (FleXLab)  \nTalk 1: On the stability of wake flows 
 past porous bluff bodies\nAbstract The characterization of wake flows is 
 typically made in the context of solid bodies. However\, often in Nature a
 nd in many practical applications\, porous media are present. The present 
 work aims at numerically investigating the effect of the porosity and perm
 eability on the wake patterns of porous bluff bodies at low-moderate Reyno
 lds numbers. This study is developed in the framework of direct numerical 
 simulation and stability analysis. To describe the flow behavior inside th
 e porous media\, a modified Darcy-Brinkman formulation is employed\, where
  also the convective terms are retained to correctly account for the inert
 ia effects at high values of permeability. First\, the two-dimensional flo
 w past rectangular cylinders is investigated\, considering thickness-to-he
 ight ratios\, t/d\, ranging from 0.01 (at plate) to 1.0 (square cylinder) 
 (see Figure 1a). The cases of the flow past a sphere and a disk are then s
 tudied\, both for the first steady and the second unsteady bifurcation. Th
 e results show that the permeability of the bodies has a strong effect in 
 modifying the characteristics of the flow instabilities\, while the porosi
 ty weakly affects the flow patterns. In particular\, the fluid flows throu
 gh the porous bodies and thus\, increasing the permeability\, the recircul
 ation regions detach from the body first and then disappear in the near wa
 kes. Moreover\, for all the configurations here investigated\, critical va
 lues of the permeability have been identified above which any instabilitie
 s are prevented\, at least in the parameters' space considered. As an exam
 ple\, Figure 1b shows the stability neutral curve (red line) for the case 
 of the rectangular cylinder with t/d=0.25\, together with the iso-contour 
 of recirculation length L = 0 (black line) that delimits the solutions wit
 h detached and no recirculation regions.\n\nTalk 2: Deformation of perfora
 ted elastic sheets due to the hydrodynamic loading by a viscous fluid\nAbs
 tract From spider webs and insect wings\, to wire fences and parachutes\,
  Nature and technology provide us with vast examples of perforated flexibl
 e structures that undergo elastic deformation due to fluid flow. Whereas f
 luid flow through porous media has been studied extensively\, the fluid-st
 ructure interactions of a perforated slender elastic object that undergoes
  large deformations due to the hydrodynamic loading of a surrounding visco
 us fluid has received much less attention. Here\, we use precision desktop
  experiments to focus on the prototypical problem of a perforated elastic 
 plate moving through a viscous fluid\, at low to moderate Reynolds number.
  We seek to provide a predictive framework for the deformation of perforat
 ed plates due to hydrodynamic loading to rationalize our experimental find
 ings. For this purpose\, we use a reduced theoretical model based on Kirch
 hoff-Euler beam theory coupled with a low Reynolds number description for 
 the fluid forcing. Specifically\, we quantify the effect of the interplay 
 between elasticity\, permeability\, and viscous loading on the deformed sh
 ape of the structure. We hope that our findings may lead to a better under
 standing of fluid-structure interactions between slender porous structures
  and viscous flows\, across biological and technological applications.
LOCATION:ME B1 B10 https://plan.epfl.ch/?room=MEB1B10
STATUS:CONFIRMED
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