Evaluation AC7-04

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A pulsatile 3D flow relevant to thoracic hemodynamics: CFD - 4D MRI comparison

Application Challenge AC7-04   © copyright ERCOFTAC 2021

Evaluation - Comparison of Test Data and CFD

The comparisons between the post-processed MRI images and downsampled CFD were done on the MRI grid on which both velocity fields are expressed.

Qualitative comparison

First a qualitative comparison between the corrected MRI velocity data and the downsampled CFD is shown in several planes of interest. In Fig. 9 the velocity field along its three components as well as the magnitude of the velocity are presented in the coronal plane. The velocity field along the X-direction ($u$-component, see Fig. 5 for the definition of the axis) is also shown in a plane along the middle of the collateral (Fig. 10) and in the cross-section in the middle of the bend (Fig. 11). These maps are given for four time instants: peak systole, peak diastole and the time instants in between. Similar velocity patterns are seen even in complex flow regions. Both CFD and MRI succeed in capturing main flow features, such as the small separation region in the main branch at peak systole and the recirculation in the aneurysm and the back flow in the bifurcation at peak diastole. Through-plane velocity comparison ($v$-component) shows larger visual discrepancies, which was expected given the low signal amplitudes collected in the MRI scanner due to the low velocities in this direction.

Figure 9: Qualitative comparison in the coronal plane

Figure 10: Qualitative comparison across the collateral - Velocity along the X-direction

Figure 11: Qualitative comparison in the cross-section of the bend - Velocity along the X-direction

L2-norm error

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Contributed by: Morgane Garreau — University of Montpellier, France

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© copyright ERCOFTAC 2021