In July 2026, I travelled to Heidelberg, Germany, together with Jakob and Kai from our group to present at TSFP14, the 14th International Symposium on Turbulence and Shear Flow Phenomena. Among the highlights was our talk on uncovering the turbulent dynamics of stenotic (narrowed) blood flow directly from 4D-flow MRI measurements — global linear stability and resolvent analysis enabled by FELiCS.
**Uncovering turbulent dynamics in stenotic flows from 4D-flow MRI.** Together with H. Dillinger and S. Schmitter from PTB Braunschweig and Berlin, and Simon Demange and Kilian Oberleithner from our lab, I presented a hybrid experimental-computational framework that couples in vitro 4D-flow MRI measurements with data assimilation and linear modeling. We 3D-printed an idealized, severely narrowed stenosis phantom and measured its mean velocity field in vitro using 4D-flow MRI at a Reynolds number of 3960. Because MRI velocity fields are noisy and corrupted by a displacement artifact, we used a physics-informed neural network in a two-step optimization to first correct the artifact and then assimilate the unknown mean pressure and eddy-viscosity fields, turning the raw scan into a RANS-consistent mean flow. That assimilated mean flow then served as the base state for global linear stability and resolvent analysis in FELiCS, revealing a stationary, positive-growth-rate eigenmode inside the recirculation bubble — consistent with a Coanda-type jet-pinching instability — and a broadband pseudo-resonance tied to the convective Kelvin–Helmholtz instability of the separated shear layer. The work demonstrates, for the first time, that linear stability tools can be applied directly to non-invasive 4D-flow MRI data, opening the door to studying instability mechanisms in real cardiovascular flows without requiring optical or physical access.
This project relied on FELiCS for both the global stability and resolvent computations on the assimilated mean flow.
Many thanks to the organizers for a fantastic symposium in such a beautiful setting!