Aortic valve leaflet fluttering is a phenomenon that can occur during systolic phases. Recent studies tend to prove that leaflet oscillations can significantly deteriorate valve durability and disturb blood flow[1]. In this context, a parametric study on the geometry of a bioprosthetic aortic valve is performed, by focusing on fluid-structure interaction phenomona. Variations in leaflet attachment curve and belly curvature are investigated. To address the complex and deforming geometry of aortic leaflets, an immersed boundary method (IBM) is coupled with a Lattice Boltzmann solver (ProLB) based on the Hybrid Recursive Regularized (HRR) collision model[2], and a finite element solver (CalculiX), using an explicit coupling algorithm between the fluid and solid solvers[3]. A bioprosthetic aortic valve is immersed in a rigid cylindrical aorta with three spherical sinuses, and a complete valve opening cycle is simulated. The complex valve structure is modeled using a hyperelastic and anisotropic constitutive law, while blood is approximated as a Newtonian fluid. Leaflet flutter amplitude and frequency, mechanical stresses, and upstream blood velocity are analyzed numerically.The results show the existence of a critical leaflet surface area beyond which large-amplitude fluttering occurs, significantly disturbing the blood flow at each oscillation period. Mechanical stresses on the valve are also strongly altered, leading to a complete reversal of curvature at the center of the leaflet belly. Such “abnormal” belly curvature is known to be detrimental to valve leaflets and may accelerate structural degradation[4]