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Item type:Publication, Access status: with files , Adaptive tolerances for staggered solution algorithms in fluid-structure interaction(Springer, 2026); ; ; ; Staggered solution algorithms are a well-known alternative to monolithic approaches for solving strongly coupled multi-field problems. A coupling between the subproblems is achieved by exchanging coupling quantities between the solvers. Implicit coupling schemes are realized by letting the solvers solve each load or time step repeatedly until convergence up to a given coupling tolerance is achieved. In fluid-structure interaction as well as a variety of other problem classes, the equations governing the individual fields are nonlinear. Accordingly, each solver performs an inner iterative solution procedure that terminates once an inner tolerance is reached. The basic idea of this work builds on the possibility to adaptively adjust these inner tolerances based on carefully designed rules while preserving the black-box nature of the solvers. The resulting coupling scheme yields significant improvements in computational efficiency compared to classical schemes where the inner solver tolerances are held fixed. This is demonstrated in several numerical examples. The idea is tested in combination with state-of-the-art convergence acceleration schemes and can be realized within any staggered solution approach by only minor modifications to the participating solvers.Publicationtype: Journal Article56 26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Parameter-free shape optimization: Various shape updates for engineering applications(Multidisciplinary Digital Publishing Institute (MDPI), 2023-08-25); ; ; ;Suchan, TimIn the last decade, parameter-free approaches to shape optimization problems have matured to a state where they provide a versatile tool for complex engineering applications. However, sensitivity distributions obtained from shape derivatives in this context cannot be directly used as a shape update in gradient-based optimization strategies. Instead, an auxiliary problem has to be solved to obtain a gradient from the sensitivity. While several choices for these auxiliary problems were investigated mathematically, the complexity of the concepts behind their derivation has often prevented their application in engineering. This work aims to explain several approaches to compute shape updates from an engineering perspective. We introduce the corresponding auxiliary problems in a formal way and compare the choices by means of numerical examples. To this end, a test case and exemplary applications from computational fluid dynamics are considered.Publicationtype: Journal ArticleScopus© Citations 2 61 179 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A fluid-structure interaction study of hemodynamics in arterial bypass-graft anastomoses(2022-06); ; ; This paper reports on numerical experiments on arterial bypass-graft anastomoses. Bypass-grafts are oftentimes used in surgical procedures to divert blood around narrowed or occluded parts of an artery. The diverted blood flow is crucial to the success of the operation as it may lead to undesirable peculiarities that can result to a renewed occlusion in the distal connection of the graft. However, an a priori prediction of detrimental hemodynamic aspects due to undesirable flow properties is difficult to perform in vitro or in vivo conditions. To this end, this work targets to enhance our understanding of harming mechanisms through in silico experiments using computational fluid dynamics (CFD) and fluid-structure interaction (FSI) simulations. The latter are realized through a partitioned coupled approach which is verified for a 2D benchmark case against literature-reported results. Finally, we present numerical results on grafts with different cuff sizes. Wall shear stress (WSS), oscillatory shear index (OSI) and hemolysis are monitored and compared in the context of either rigid or elastic walls and cuff sizes. Special interest is given to the prediction of hemolysis induction which is often not considered in such studies. We show that wall elasticity is the key parameter in terms of WSS prediction while cuff size mainly affects the estimation of OSI.Publicationtype: Conference Paper46