Computational haemodynamics Investigation of blood flow using high-performance computing The CompHem group focuses on the development and use of high-peformance numerical tools to extract key information on blood flow in different geometrical configurations and for various applications. The main topics are thus: (i) study of the flow characteristics and instabilities downstream of flexible aortic valve (bio)prostheses implanted in aortic roots in order to optimise valve design by reducing detrimental leaflet motion such as flutter and pin-wheeling and to characterise the flow-dependent leaflet calcification process (D); (ii) study of the laminar-to-turbulent transition downstream of aortic stenoses and in realistic geometries of thoracic aortas under pulsatile conditions and for different wall properties [(B), (D)]; (iii) investigation of the flow in carotid bifurcations under pulsatile conditions to understand the role of haemodynamic factors on atherosclerosis formation [(A), (D)]; (iv) comprehensive modelling of the biomechanical and haemodynamic function of diseased mitral valves to help in the design of an optimised surgical repair procedure [(C), (D)]. The wide range of available tools, which are continuously developed and optimised to work on high-performance-computing (HPC) architectures allows us to perform simulations of fluid-structure interaction (FSI) problems, data-driven flow simulations and GPU-distributed large-scale simulations. The extracted in silico information is compared to in vivo 4D Flow Magnetic Resonance Imaging (MRI) measurements and to in vitro results obtained from three-dimensional particle image/tracking velocimetry in order to validate numerical models and to give clinical relevance to the obtained numerical results. Results from the latest FSI studies conducted by varying leaflet shape parameters under peak systole conditions: (a) Leaflet shape with reduced belly curvature, (b) Leaflet shape with large belly curvature, (c) Leaflet shape with V-shaped scallop curve, (d) Almost static leaflet motion for the leaflet shape with reduced curvature radius (motion goes from dark black to light grey with a time interval between the instants of 0.04 s), (e) Leaflet flutter wave motion in side and top sections passing through the leaflet centre in the case of the leaflet shape with larger curvature, (f) Leaflet kinematics characterised by wave motions in the longitudinal and transversal directions for the valvular case with a V-shaped scallop curve, (g) Viscous shear stress in the flow and von Mises stress for case (a) (colorbars: viscous shear stress in Pa ranging from 0 to 8 (blue to white) and von Mises stress ranging from 35 to 10,000 Pa (black to red)), (h) Viscous shear stress and von Mises stress for case (b), (i) Viscous shear stress and von Mises stress for case (c), (j, k, l) Coherent vortical structures for cases (a, b, c) highlighted by iso-surfaces of negative second eigenvalue of the sum of the squared strain-rate and rotation-rate tensor. Schliessen Current contributors: Ali Mokhtari (PhD student) (A), Karoline-Marie Bornemann (PhD student) (B), Valérie Kulka (PhD student) (C), Dr Pascal Corso (PostDoc, Head of CompHem group) (D). Collaborations: Institute of Computational Science, Università della Svizerra italiana (USI); Biomedical Imaging/Cardiovascular Magnetic Resonance, ETHZ; Biomedical Image Computing/Computer Vision Laboratory, ETHZ; Nanoparticle Systems Engineering Lab, ETHZ/EMPA; Sacks Lab, the University of Texas at Austin. Projects: PASC AV-FLOW (2014-2017), PASC HPC-PREDICT (2017-2021), SNSF-DFG Carotis (2021-2024), PASC MitrAccel (2021-2024). Former members: Dr Barna Becsek - Dr Dario De Marinis (researcher at the Politecnico di Bari) - Dr Hadi Zolfaghari (SNSF postdoctoral fellow at the University of Cambridge).