Flow diverter stents simulation with CFD: porous media modelling Nicol´ as Dazeo 1 , Javier Dottori 1 , Gustavo Boroni 1 , Alejandro Clausse 1 , and Ignacio Larrabide 1 1 Instituto PLADEMA, CONICET, UNICEN, Tandil, Argentina ABSTRACT Intracranial aneurysm treatment with flow diverters stent (FDs) is a minimally invasive approach for use in human patients. Because this treatment is strongly related to blood flow, flow simulation by CFD is an attractive method to study FDs. Such flow simulations generally define geometries of aneurysms and stents in the computation by creating calculation meshes in the fluid space. For the other hand, generating a mesh in porous media (PM) sometimes represents a smaller computational load than generating realistic stent geometries with CFD, particularly for the small gaps between stent struts. For this reason, PMs become attractive to simulate FDs. To find the proper parameters, we investigated Darcy-Forchheimer model for porous media. The model describes the relation between the pressure drop and flow velocity considering a viscous permeability (linear model’s term), and an inertial permeability (quadratic model’s term). Finally, two stage studies were performed. First, we verified flow model validity at different angles in known flow conditions. Second, model validation was checked for a channel with no-slip boundary conditions. Results indicate that resistance calculated according to model has a difference of less than 3.5 % which is appropriate to characterize the FDs. Keywords: Intracranial Aneurysm, Flow Diverter Stent, CFD, Porous Media 1. INTRODUCTION Intracranial Aneurysms (IA) are pathological dilatations of arteries inside the skull, which may rupture if not treated on time. The rupture of an IA follows by subarachnoid hemorrhage with high morbidity and mortality rates [1]. Feasible treatments for IA are intravascular stents and coils. In the last decade, the use of intravascular stents become more frequent in such pathologies. Flow Diverters stents (FDs) are made of braided threads of a shape memory alloy, typically Nitinol. Their design is radically different from conventional stents. In particular, FDs are characterized by very thin wires (∼40 μm), very small pores (∼310 μm 2 ) and a single or multi-layer structure. These devices are becoming more and more used in the treatment of IA [2, 3]. Still, there are many aspects of their behavior and effect on local hemodynamics that are yet not fully understood. The use of Computational Fluid Dynamics (CFD) can be of great benefit to understand the effect and implications of their use [4, 5, 6]. Due to its complex geometrical structure, modeling devices like stents, FDs and coils imposes a number of limitations and requires a considerable computational effort for the simulation of relatively small fluid domains. This calls to Porous Medium (PM) modelling to reduce time consuming. Similar strategies were previously used in different treatments [7]. FD porosity is a major feature driving their ability to modify local aneurysmal flow [8]. Because of this, seems natural to model such devices using a PM mode. Interestingly, porosity is determined not only by the FDs geometry, but also by the final position and deployment in the vessel. Karmonik et al. [9] demonstrate that a PM model with arbitrary parameters of a FD presents a decrease in velocities and Wall Shear S tress (WSS) in the aneurysm sac. Augsburger et al. [10] compared the simulation of two IA with a full FD model and a PM model. This approach requires a previous simulation of the FD with a Direct Numerical Simulation (DNS) model in an isolated simulation to determine PM parameters. First, we analyze pressure drops over DNS with idealized geometries (channel). PM coefficients are calculated from DNS results. PM model verification is obtained by comparing with DNS simulation. Then, the proposed model is validated against DNS using no-slip conditions. Furthermore, we study the impact of FDs parameters to the PM.