Immersed Methods for Fluid-Structure-Contact- Interaction Simulations and Complex Geometries

Fluid-structure-contact interaction (FSCI) is a common phenomenon in various computational science application fields, such as bio-medicine or engineering. Simulations of such interaction account for the mechanics of fluids, structures, and their interaction but also resolve the contact problem between the structures. The latter may include contact among elastic structures and their interaction with rigid obstacles or artificial barriers. In the aforementioned application fields, correctly modeling turbulence is essential for describing the dynamics at the interface between solid and fluid domains.In this context, the ability to handle complex geometric features while maintaining high fidelity of the results is an essential property of FSCI and its subtopics. For example, such features may arise in the solid mesh from real-world geometric models or highly-detailed and noisy volume/surface geometries acquired from real-world data (e.g., synchrotron x-ray imaging). Furthermore, complex mesh models combined with large deformations and many-body interactions give rise to challenging simulation scenarios and require numerical techniques and algorithms that are robust, flexible, and at the same time, adequately describe the physics with the required fidelity.In the current state of the art in computational fluid-structure-interaction (FSI), we find Arbitrary-Lagrangian-Eulerian (ALE) and immersed techniques. In ALE, the fluid mesh deforms with the structure mesh to guarantee an accurate treatment of the FSI interface. A pure ALE approach would be impractical in scenarios where large deformation and contact interactions must be simulated. This impracticality is due to vanishing fluid gaps and highly distorted mesh elements. On the contrary, immersed methods are suitable candidates for handling such cases. In fact, immersed techniques describe the structure mesh separately and allow to embed structures subject to large deformations into an Eulerian, with the cost of greater resolution requirements over ALE. Immersed boundary (IB) is suitable to handle thin surfaces, while immersed domain (ID) can also naturally handle thick surfaces and steeper gradients in the coupled fields. ID also fits well into a monolithic optimization framework for solving the FSI problem. However, the applicability of ID methods has been mostly demonstrated for relatively simple cases and geometries without considering complex contact interactions, the modeling of turbulent flows, or proper discretization for local mass conservation. In particular, the near-wall region modeling is not completely addressed in the related literature. Here, the interaction of turbulence wall effects, contact, and solid boundaries play a crucial role in the accuracy of the numerical prediction.To this end, our research will aim at improving the current state of the art by developing and studying an immersed domain technique for FSCI simulations in complex geometries and turbulent flows. The proposed model adopts a monolithic formulation in conjunction with the Control Volume Finite Element Method (CVFEM) fluid formulation with a special treatment of the fluid-solid interface, proposing new turbulence modeling techniques for immerse domain FSCI. The procedures will also employ parallel, automatic, and robust mortar-based contact detection and discretization procedures that can handle many immersed structures described by arbitrarily distributed meshes on modern supercomputers and the ability to perform scale resolving simulations (SRS). We will perform detailed numerical studies to study and illustrate our methods’ quality against present tools and techniques, followed by comparisons with experimental measurements and parallel scaling studies. As a result of this project, we expect to realize robust methods, numerical algorithms, and transparent workflows for studying FSCI.The impact of this project will be twofold. First, properly modeling significant effects, such as turbulence, is essential for generating credible simulation results for real-world applications. The developed methodologies will have the ambition to be practical and reliable tools for engineers and their designs in several fields. Second, as such studies require a supercomputing approach, they will drive the development of efficient and scalable open-source software components that will improve current and prospective scientific computing projects for our respective laboratories and collaborations.