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SUMMARY:MEchanics GAthering -MEGA- Seminar: Experimental and numerical ins
 ights into laminar-turbulent transition mechanisms in bioprosthetic aortic
  valves
DTSTART:20241114T161500
DTEND:20241114T170500
DTSTAMP:20260502T145436Z
UID:b9c371b4f6eebfd8251c217df2260f1f7687fa487c7490a600cf3821
CATEGORIES:Conferences - Seminars
DESCRIPTION:Karoline Marie Bornemann\, Lorenzo Ferrari (ARTORG\, UniBe)\nA
 bstract: Aortic valve replacement with a valve prosthesis is necessary wh
 en the native valve is compromised. Turbulent flow is known to occur in th
 e ascending aorta during peak systole in patients with bioprosthetic heart
  valves (BHV) which negatively affects performance and limits BHV durabili
 ty. To mitigate these adverse effects of valve turbulence\, we aim to bett
 er understand the three-dimensional laminar-turbulent transition mechanism
 s past BHV. Depending on their design and the flow conditions\, the valve 
 leaflets may exhibit periodic oscillations – so-called leaflet flutterin
 g – making this a complex fluid-structure interaction\nproblem.\nThe fir
 st part of the talk focuses on experimental investigations of laminar-turb
 ulent transition past BHV at different flow rates. A pulse duplicator simu
 lated physiological conditions at\ncardiac outputs (COs) of 2\, 3\, 4\, an
 d 5 L/min. Flow fields were assessed in a generalized aortic model using b
 oth 2D particle image velocimetry (2D-PIV) and 3D scanning PIV. Recordings
  at different magnifications were performed to resolve different flow stru
 ctures and to quantify small leaflet oscillations. Vortex shedding and lea
 flet fluttering are discussed in relation to the flow conditions.\nThe sec
 ond part of the talk addresses numerical investigations of laminar-turbule
 nt transition past different designs of BHVs. We conduct high-fidelity flu
 id-structure interaction (FSI)\nsimulations of a generic aortic root with 
 inserted fibre-reinforced biological tissue valve. The fluid motion is mod
 elled by a Direct Numerical Simulation approach and coupled to the\nstruct
 ural solver by a modified Immersed Boundary Method. To assess the influenc
 e of leaflet fluttering on transition mechanisms\, we compare a non-flutte
 ring to a fluttering valve design. Vortex development and breakdown as wel
 l as quantities such as turbulent kinetic energy distribution or viscous s
 hear stresses are assessed in comparison revealing significant differences
  in mechanisms of laminar-turbulent transition. By assessing fundamental l
 aminar-turbulent transition mechanisms using both experimental and numeric
 al approaches\, we contribute to improved valve design and optimal valve p
 ositioning towards targeted control of the onset of turbulence and a more 
 favourable outcome for the patient.\n\nBio: Karoline-Marie Bornemann rece
 ntly graduated with a PhD in Biomedical Engineering from the ARTORG Center
  for Biomedical Engineering Research at the University of Bern in\nSwitzer
 land. She completed her master studies in Mechanical Engineering with spec
 ialization Aerospace Engineering at the Technische Universität Dresden in
  Germany\, during which she spent 9 months as a visiting student at the Un
 iversity of Melbourne in Australia. Recently\, she performed a PhD secondm
 ent in the FLOW group at the Royal Institute of Technology (KTH) in Stock
 holm\, Sweden. Using high-fidelity numerical fluid-structure interaction s
 imulations and tools of stability analysis\, she investigates fundamental 
 instability mechanisms leading to laminar-turbulent transition past biopro
 sthetic aortic valves.\nLorenzo Ferrari is concluding his PhD in Biomedica
 l Engineering at the ARTORG Center for Biomedical Engineering Research at 
 the University of Bern in Switzerland. After completing\nhis Master’s at
  Politecnico di Milano in Biomechanics and Biomaterials\, he worked for 9 
 months as a research assistant at EPFL\, evaluating cardiac assist devices
  in-vivo and in-vitro.\nEarlier this year\, he performed a PhD secondment 
 at the Physics of Fluids (POF) group at the University of Twente (UT) in t
 he Max Planck Center for Complex Fluid Dynamics. Combining high-speed came
 ra recordings with velocimetry techniques\, he characterizes different typ
 e of valve prothesis under different hemodynamic conditions.
LOCATION:MED 1 1518 https://plan.epfl.ch/?room==MED%201%201518 https://epf
 l.zoom.us/j/67041786969?pwd=a1lXa3lsVGpvL1VpN2RDR2l4clg0QT09
STATUS:CONFIRMED
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