Visualizing multiphysics, fluid-structure interaction phenomena in intracranial aneurysms

Abstract

This work presents recent advances in visualizing multi-physics, fluid-structure interaction (FSI) phenomena in cerebral aneurysms. Realistic FSI simulations produce very large and complex data sets, yielding the need for parallel data processing and visualization. Here we present our efforts to develop an interactive visualization tool which enables the visualization of such FSI simulation data. Specifically, we present a ParaView-NekTar interface that couples the ParaView visualization engine with NekTar's parallel libraries, which are employed for the calculation of derived fields in both the fluid and solid domains with spectral accuracy. This interface allows the flexibility of independently choosing the resolution for visualizing both the volume data and the surface data from each of the solid and fluid domains, which significantly facilitates the visualization of complex structures under large deformations. The animation of the fluid and structure data is synchronized in time, while the ParaView-NekTar interface enables the visualization of different fields to be superimposed, e.g. fluid jet and structural stress, to better understand the interactions in this multi-physics environment. Such visualizations are key towards elucidating important biophysical interactions in health and disease, as well as disseminating the insight gained from our simulations and further engaging the medical community in this effort of bringing computational science to the bedside.

Keywords: Blood flow; Cerebral aneurysms; Fluid-structure interactions; High performance computing; Parallel visualization.

Fig. 1

Flow-structure interactions in an aneurysm. Shown on the left is the patient-specific cranial arterial network where the spectral element equations are solved. Shown in the inset ( top ) is the structure domain representing the elastic tissue of the aneurysm wall. Shown in the inset ( bottom ) is the local stress field in the aneurysm wall due to interactions with recirculating blood flow.

Fig. 2

Illustration of the unstructured surface grid and the polynomial basis employed in NekTar. The solution domain is decomposed into non-overlapping elements. Within each element the solution is approximated by vertex, edge, face and (in 3D) interior modes. The shape functions associated with the vertex, edge and face modes for fourth-order polynomial expansion defined on triangular and quadrilateral elements are shown in color. (For interpretation of the references to colour in this figure text, the reader is referred to the web version of this article).

Fig. 3

This image shows Lambda2 calculated without projection (A) and with (B).

Fig. 4

Strong scaling performance of the stress tensor calculation for solid domains in the ParaView–NekTar reader plug-in.

Fig. 5

Illustrations of the application of mesh displacement. (A) shows the original mesh. (B) shows the deformed mesh due to fluid flow. (C) shows both meshes together to highlight their differences. In tile (D) the values of the displacement have been scaled to accentuate the effect.

Fig. 6

Blood flow in a compliant cerebral aneurysm containing blood flow streamlines (colored by velocity magnitude), and stress tensor magnitude on the walls of the artery. Arrow glyphs along the streamlines indicate the direction of the flow. (For interpretation of the references to colour in this figure text, the reader is referred to the web version of this article).

Fig. 7

Blood flow in a compliant cerebral aneurysm containing blood flow streamlines (colored by velocity magnitude), and stress tensor magnitude on the walls of the artery. Isocontours of the vorticity magnitude, which indicate areas of swirling flow, are colored by the pressure. (For interpretation of the references to colour in this figure text, the reader is referred to the web version of this article).