MEchanics GAthering -MEGA- Seminar: Experimental and numerical insights into laminar-turbulent transition mechanisms in bioprosthetic aortic valves
Event details
| Date | 14.11.2024 |
| Hour | 16:15 › 17:05 |
| Speaker | Karoline Marie Bornemann, Lorenzo Ferrari (ARTORG, UniBe) |
| Location | Online |
| Category | Conferences - Seminars |
| Event Language | English |
Abstract: Aortic valve replacement with a valve prosthesis is necessary when the native valve is compromised. Turbulent flow is known to occur in the ascending aorta during peak systole in patients with bioprosthetic heart valves (BHV) which negatively affects performance and limits BHV durability. To mitigate these adverse effects of valve turbulence, we aim to better understand the three-dimensional laminar-turbulent transition mechanisms past BHV. Depending on their design and the flow conditions, the valve leaflets may exhibit periodic oscillations – so-called leaflet fluttering – making this a complex fluid-structure interaction
problem.
The first part of the talk focuses on experimental investigations of laminar-turbulent transition past BHV at different flow rates. A pulse duplicator simulated physiological conditions at
cardiac outputs (COs) of 2, 3, 4, and 5 L/min. Flow fields were assessed in a generalized aortic model using both 2D particle image velocimetry (2D-PIV) and 3D scanning PIV. Recordings at different magnifications were performed to resolve different flow structures and to quantify small leaflet oscillations. Vortex shedding and leaflet fluttering are discussed in relation to the flow conditions.
The second part of the talk addresses numerical investigations of laminar-turbulent transition past different designs of BHVs. We conduct high-fidelity fluid-structure interaction (FSI)
simulations of a generic aortic root with inserted fibre-reinforced biological tissue valve. The fluid motion is modelled by a Direct Numerical Simulation approach and coupled to the
structural solver by a modified Immersed Boundary Method. To assess the influence of leaflet fluttering on transition mechanisms, we compare a non-fluttering to a fluttering valve design. Vortex development and breakdown as well as quantities such as turbulent kinetic energy distribution or viscous shear stresses are assessed in comparison revealing significant differences in mechanisms of laminar-turbulent transition. By assessing fundamental laminar-turbulent transition mechanisms using both experimental and numerical approaches, we contribute to improved valve design and optimal valve positioning towards targeted control of the onset of turbulence and a more favourable outcome for the patient.
Bio: Karoline-Marie Bornemann recently graduated with a PhD in Biomedical Engineering from the ARTORG Center for Biomedical Engineering Research at the University of Bern in
Switzerland. She completed her master studies in Mechanical Engineering with specialization Aerospace Engineering at the Technische Universität Dresden in Germany, during which she spent 9 months as a visiting student at the University of Melbourne in Australia. Recently, she performed a PhD secondment in the FLOW group at the Royal Institute of Technology (KTH) in Stockholm, Sweden. Using high-fidelity numerical fluid-structure interaction simulations and tools of stability analysis, she investigates fundamental instability mechanisms leading to laminar-turbulent transition past bioprosthetic aortic valves.
Lorenzo Ferrari is concluding his PhD in Biomedical Engineering at the ARTORG Center for Biomedical Engineering Research at the University of Bern in Switzerland. After completing
his 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.
Earlier this year, he performed a PhD secondment at the Physics of Fluids (POF) group at the University of Twente (UT) in the Max Planck Center for Complex Fluid Dynamics. Combining high-speed camera recordings with velocimetry techniques, he characterizes different type of valve prothesis under different hemodynamic conditions.
problem.
The first part of the talk focuses on experimental investigations of laminar-turbulent transition past BHV at different flow rates. A pulse duplicator simulated physiological conditions at
cardiac outputs (COs) of 2, 3, 4, and 5 L/min. Flow fields were assessed in a generalized aortic model using both 2D particle image velocimetry (2D-PIV) and 3D scanning PIV. Recordings at different magnifications were performed to resolve different flow structures and to quantify small leaflet oscillations. Vortex shedding and leaflet fluttering are discussed in relation to the flow conditions.
The second part of the talk addresses numerical investigations of laminar-turbulent transition past different designs of BHVs. We conduct high-fidelity fluid-structure interaction (FSI)
simulations of a generic aortic root with inserted fibre-reinforced biological tissue valve. The fluid motion is modelled by a Direct Numerical Simulation approach and coupled to the
structural solver by a modified Immersed Boundary Method. To assess the influence of leaflet fluttering on transition mechanisms, we compare a non-fluttering to a fluttering valve design. Vortex development and breakdown as well as quantities such as turbulent kinetic energy distribution or viscous shear stresses are assessed in comparison revealing significant differences in mechanisms of laminar-turbulent transition. By assessing fundamental laminar-turbulent transition mechanisms using both experimental and numerical approaches, we contribute to improved valve design and optimal valve positioning towards targeted control of the onset of turbulence and a more favourable outcome for the patient.
Bio: Karoline-Marie Bornemann recently graduated with a PhD in Biomedical Engineering from the ARTORG Center for Biomedical Engineering Research at the University of Bern in
Switzerland. She completed her master studies in Mechanical Engineering with specialization Aerospace Engineering at the Technische Universität Dresden in Germany, during which she spent 9 months as a visiting student at the University of Melbourne in Australia. Recently, she performed a PhD secondment in the FLOW group at the Royal Institute of Technology (KTH) in Stockholm, Sweden. Using high-fidelity numerical fluid-structure interaction simulations and tools of stability analysis, she investigates fundamental instability mechanisms leading to laminar-turbulent transition past bioprosthetic aortic valves.
Lorenzo Ferrari is concluding his PhD in Biomedical Engineering at the ARTORG Center for Biomedical Engineering Research at the University of Bern in Switzerland. After completing
his 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.
Earlier this year, he performed a PhD secondment at the Physics of Fluids (POF) group at the University of Twente (UT) in the Max Planck Center for Complex Fluid Dynamics. Combining high-speed camera recordings with velocimetry techniques, he characterizes different type of valve prothesis under different hemodynamic conditions.
Practical information
- General public
- Free
Organizer
- MEGA.Seminar Organizing Committee