Gambit 2

The axial CTA data sets were digitally processed to extract the geometric contours of the coronary arteries. A software prototype (Siemens AG, Healthcare Sector, Forchheim, Germany) was used for semiautomatic segmentation and meshing of the vessel surface with triangles. This model was imported into an open-source software package (MeshLab V1.11). Structures other than the examined vessel were removed. Sidebranches were cut at a distance at least two vessel diameters apart from the bifurcation. The resulting surface mesh model was further processed in a commercially available software tool (Gambit 2.4.6, Ansys Inc., Southpointe, PA, USA). In a first step the previous mesh was removed and replaced by a triangular surface mesh with smaller element size. Inflow and outflow areas were defined. Subsequently an adaptive 3D computational mesh was built consisting of 300,000 to 400,000 polyhedral elements for the entire model. One model per vessel was reconstructed. This model was further used for blood flow simulations (Fig. 1).

All simulations in this paper were performed in ANSYS FLUENT 16.0 (ANSYS Inc., Canonsburg, PA, USA). In this paper, the volume of fluid (VOF) model was used to obtain the gas-liquid interface. The VOF model was employed to track the moving gas-liquid interface^{21 (link)}. The $\mathrm{k}-\omega -\mathrm{SST}$ turbulence model was used to enclose the governing equations of the fluid motion^{22 (link)}. All the boundary conditions were set to the wall. The PISO algorithm was used to solve the velocity and pressure. The time step size was 0.0001 seconds. The maximum courant number was 0.25. The grid for this hollow OSR was generated using Gambit 2.4.6 (ANSYS Inc., Canonsburg, PA, USA).