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Item type:Publication, Access status: with files , Code verification of immersed boundary techniques using the method of manufactured solutionsCode verification plays a crucial role for all finite element applications, especially for non-standard ones, such as immersed boundary approaches, which are typically based on novel algorithms and often error-prone in-house implementations. Instead of relying on rarely available analytical solutions or overkill FEM simulations, in this article, the capabilities of the method of manufactured solutions (MoMS) are explored, enabling an easy and straightforward derivation of closed-form reference solutions. The focus is kept on immersed problems, in particular, on the finite cell method (FCM), and manufactured solutions are derived for 2D and 3D problems involving voids and single/multiple inclusions. We propose several approaches for the construction of the manufactured solutions, where zero traction conditions for void regions and continuous normal stresses along material interfaces are directly fulfilled. Thus, no weak boundary conditions are required for reproducing the manufactured solution via FCM. This not only enables code verification for FCM implementations that lack the option of applying weak boundary conditions, but also keeps the simulation complexity low, when testing other relevant features, e.g., different integration schemes or the implementation of enrichment functions. The flexibility and wide application range of the MoMS in the context of immersed boundary simulations is demonstrated using static, quasi-static, and transient problems in the context of linear elasticity. Finally, the analytical derivations of the manufactured solutions used in this paper are provided as supplementary material.Publicationtype: Journal Article31 83 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Vibroacoustic simulations of acoustic damping materials using a fictitious domain approach(Elsevier, 2024-01-06); ; ; The numerical investigation of acoustic damping materials, such as foams, constitutes a valuable enhancement to experimental testing. Typically, such materials are modeled in a homogenized way in order to reduce the computational effort and to circumvent the need for a computational mesh that resolves the complex micro-structure. However, to gain detailed insight into the acoustic behavior, e.g., the transmittance of noise, such fully resolved models are mandatory. The meshing process can still be drastically simplified by using a fictitious domain approach. We propose the finite cell method, which combines the fictitious domain approach with high-order finite elements and resolves the complex geometry using special quadrature rules. In order to take into account the fluid-filled pores of a typical damping material, a coupled vibroacoustic problem needs to be solved. To this end, we construct two separate finite cell discretizations and prescribe coupling conditions at the interface in the usual manner. The only difference to a classical boundary fitted approach to vibroacoustics is that the fluid-solid interface is immersed into the respective discretization and does not correspond to the element boundaries. The proposed enhancement of the finite cell method for vibroacoustics is verified based on a comparison with commercial software and used within an exemplary application.Publicationtype: Journal Article13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Octree-based integration scheme with merged sub-cells for the finite cell method : application to non-linear problems in 3D(Elsevier, 2022-09-30); ; ; ; Fictitious domain methods, such as the Finite Cell Method (FCM), allow for an efficient and accurate simulation of complex geometries by utilizing higher-order shape functions and an unfitted discretization based on rectangular elements. Since the mesh does not conform to the geometry, cut elements arise that are intersected by domain boundaries. For optimal convergence rates and the efficiency of the simulation in general, special integration schemes have to be used in such elements. In this contribution, the often used, robust octree-decomposition-based integration scheme is enhanced by a novel approach reducing the computational effort when evaluating the discontinuous integrals. This is realized by introducing an additional step, in which the local integration mesh is simplified using data compression techniques leading to fewer integration domains/points. An important advantage of the proposed method is that it can be added in a modular fashion to already existing codes. While it inherits all desired properties of the octree-decomposition-based integration scheme, it significantly reduces the number of integration points and has hardly any negative effect on the simulation accuracy. In this paper, the proposed integration scheme is introduced in detail, and investigated by means of numerical examples in the context of 3D non-linear problems.Publicationtype: Journal ArticleScopus© Citations 9 62 441