In order to reduce the complexity of heart hemodynamics simulations, uncoupling approaches are often considered for the modeling of the immersed valves as an alternative to complex fluid‐structure interaction (FSI) models. A possible shortcoming of these simplified approaches is the difficulty to correctly capture the pressure dynamics during the isovolumetric phases. In this work, we propose an enhanced resistive immersed surfaces (RIS) model of cardiac valves, which overcomes this issue. The benefits of the model are investigated and tested in blood flow simulations of the left heart where the physiological behavior of the intracavity pressure during the isovolumetric phases is recovered without using fully coupled fluid‐structure models and without important alteration of the associated velocity field.

The numerical simulation of a thin-walled structure immersed in an incompressible fluid can be addressed by various methods. In this paper, three of them are considered: the Arbitrary Lagrangian-Eulerian (ALE) method, the Fictitious Domain/Lagrange multipliers (FD) method and the Nitsche-XFEM method. Taking ALE as a reference, the advantages and limitations of FD and Nitsche-XFEM are carefully discussed on three benchmark test cases which have been chosen to be representative of typical difficulties encountered in valves or living cells simulations. Résumé :La simulation numérique d'une structure mince immergée dans un fluide incompressible peutêtre abordée par différentes méthodes. Dans cet article, trois d'entre elles sont considérées: la méthode Arbitrairement Lagrangienne Eulérienne (ALE), la méthode de domaine fictif avec multiplicateurs de Lagrange (FD) et la méthode Nitsche-XFEM. En prenant la méthode ALE comme référence, les avantages et les limites des méthodes FD et Nitsche-XFEM sont soigneusement discutés sur trois cas tests qui ontété choisis pourêtre représentatifs des difficultés typiques rencontrées dans les simulations de valves ou de cellules. Mots-clés :interaction fluide-structure, fluide incompressible, structure mince immergée, maillages non compatibles, maillages compatibles, méthode de domaine fictif, méthode XFEM, méthode de Nitsche, méthode ALE.

Fictitious domain approximations of fluid-structure interaction problems are generally discretized in time using strongly coupled schemes. This guarantees unconditional stability but at the price of solving a computationally demanding coupled system at each time-step. The design of loosely coupled schemes (i.e., methods that invoke the fluid and solid solvers only once per time-step) is of fundamental interest, especially for three-dimensional simulations, but the existing approaches are known to suffer from severe stability and/or time accuracy issues. We propose a new approach that overcomes these difficulties in the case of the coupling with immersed thin-walled structures.

The simulation of cardiac blood flow using patient-specific geometries can help for the diagnosis and treatment of cardiac diseases. Current patient-specific cardiac flow simulations requires a significant amount of human expertise and time to pre-process image data and obtain a case ready for simulations. A new procedure is proposed to alleviate this pre-processing by registering a unique generic mesh on patient-specific cardiac segmentations and transferring appropriately the spatiotemporal dynamics of the ventricle. The method is applied on real patient data acquired from 3D ultrasound imaging. Both a healthy and a pathological conditions are simulated. The resulting simulations exhibited physiological flow behavior in cardiac cavities. The experiments confirm a significant reduction in pre-processing work.