Two-Way Strongly Coupled Fluid-Structure Interaction Simulations with OpenFOAM
1Polytechnique Montréal, Canada; 2Andritz Hydro, Canada
Analysing the interaction between a vibrating immersed solid body and its surrounding fluid, also known as fluid-structure interaction (FSI) analysis, constitutes a broad field of research with many applications in science and engineering. Among these applications, the study of the dynamic response of submerged structures in flowing water presents specific challenges related to the non-negligible density of the fluid, which induces a significant added-mass effect. In such systems, mutual effects of the solid on the fluid movement and of the fluid on the solid response must be considered in order to accurately predict the dynamic behavior of the system as a whole. Numerical simulations of these systems hence impose a tight coupling of the fluid and solid simulations through bidirectional transfer of information through the interface between the domains.
This presentation explores the development and validation of an integrated FSI solver based on OpenFOAM fluid and structural analysis capabilities to perform FSI simulations using a fully coupled formulation. In order to validate the developed solver, a coupled validation case is discussed, and results are compared to references data obtained using a commercial solver and results published in literature. The validation test case consists of a plate fixed in a closed box and excited by an initial pressure force. The surrounding fluid damps the displacements of the plate and oscillations disappear. A second test case is also simulated, and results are compared to experimental measurements realized by Andritz. This test case consists of a profiled plate placed in a water tunnel and excited using piezoelectric actuators. Measurements were carried out for several flow conditions and three distinct profiles with varying aspect ratios. Two types of validations are performed, first with experimental data and also with previously computed results using a commercial solver.
Analysis of finite volume solution algorithms for solid mechanics implemented in OpenFOAM
University College Dublin, Ireland
Since its inception, OpenFOAM has included solvers for solid mechanics based on the finite volume method, for example, solidDisplacementFoam. The adopted solution procedures were inspired by a number of prior developments within the finite volume computational solid mechanics field. An in-depth review of the finite volume method for solid mechanics can be found in a recent preprint article by Cardiff and Demirdžić. The current work examines a number of solid mechanics cell-centred discretisations and solution algorithms implemented in OpenFOAM, in terms of accuracy, efficiency and robustness, with the aim of providing insight into the relationship between the differing approaches.
A variety of finite volume formulations have been developed for the solution of solid mechanics problems, with differences in terms of discretisation, solution methodology and overall philosophy. Approaches can be classified in a number of ways, for example, based on the: spatial distribution of the primitive variables: cell-centred vs vertex-centred vs staggered- grid; solution algorithm: implicit (solution of a linear system) vs explicit (matrix-free); or stabilisation approach: Rhie-Chow vs Jameson-Schmidt-Turkel vs Godunov methods.
Considering boundary value problems governed by the conservation of linear momentum in Lagrangian integral form, a variety of cell-centred discretisations and related solution methodologies may be employed. For example, formulations may be based on: an unknown displacement vector solved using an implicit segregated or coupled approach; an unknown displacement vector and unknown pressure solved using an implicit segregated or coupled (or partly-coupled) approach; or an unknown displacement vector solved using a fully explicit matrix-free approach.
In the current study, a number of these formulations and their implementations will be examined on a variety of benchmark cases.
Development And Validation Of An Immersed-Boundary Solver For Fluid-Structure Interaction In Polymer Extrusion Equipment
Institut für Kunststoffverarbeitung an der RWTH Aachen, Germany
Products extruded from a polymer melt are widely used in packaging and infrastructure applications. The key to ensuring product quality is the usage of finely tuned extrusion equipment, including both the feedscrew and the extrusion die.
Recent research has shown that there is a significant thermal interaction between the polymer melt and the extrusion die. In some applications, the high pressure of the extrusion process leads to a geometric deviation in the extrusion die. Both effects can cause product quality to deteriorate, which is why integrative simulation techniques are used to predict them. These techniques link the simulation model of the fluid melt with a simulation model of the solid die.
However, for efficient (automatic) geometric optimization to take place, the effort required to set up a new calculation consisting of multiple geometries and multiple physical models must be reduced. We therefore present a solver set-up that enables quick geometric updates in optimization problems concerning flows in polymer extrusion equipment. This novel method captures both thermal and mechanical interactions between the polymer melt and the metal of the equipment.
Based on an Immersed Boundary approach, the solver calculates temperatures, mechanical stresses etc. on the whole grid, meaning that the distinction between fluid and solid only is made by a variation of the local properties of flow resistance, thermal diffusivity, elastic modulus, etc.. Therefore, creating a new geometry is just a matter of setting up new fields instead of creating a new mesh.
In this work, the solver is benchmarked against both analytical solutions and conventional, non-immersed numerical calculations and found perform well.
Block-coupled finite volume solver for incompressible linear elasticity
1University of Zagreb, Faculty of Mechanical Engineering and Naval Archtecture, Croatia; 2University College Dublin, School of Mechanical and Materials Engineering, Ireland
A finite volume solver for predicting the linear elastic behavior of an incompressible elastic solid is proposed in [I. Bijelona, I. Demirdzic and S. Muzaferija. A finite volume method for incompressible linear elasticity. Computer Methods in Applied Mechanics and Engineering, 195(44-47):6378-6390, 2006.], where the incompressibility constraint is enforced by employing the hydrostatic pressure as an additional variable and SIMPLE based segregated solution procedure is used to solve resulting set of coupled algebraic equations. In this paper, the above described solver is extended by implementing a block-coupled solution procedure similar to one used for incompressible fluid flow [T. Uroic and H. Jasak. Block-selective algebraic multigrid for implicitly coupled pressure-velocity system. Computers & Fluids, 67:100-110, 2018.]. Although with such approach the substantial improvement of the computational efficiency is obtained, the major problem of finite volume stress analysis related to strong inter-displacement-component coupling is still present.
Coupling OpenFOAM to different solvers, physics, models, and dimensions using preCICE
1Technical University of Munich, Germany; 2Eindhoven University of Technology
OpenFOAM provides a rich arsenal of single-physics solvers, while other software projects also offer a wide range of solvers for structural dynamics or heat transfer. Moreover, packages for special applications, such as nuclear reactor safety, hemodynamics, or flood simulations need to integrate 3D flow phenomena into their workflow, which is often built around 1D or 2D models.
The coupling library preCICE for partitioned multi-physics simulations can bring together different solvers, in a minimally invasive way. It allows them to communicate via MPI ports or TCP/IP sockets, it maps the boundary values using advanced methods such as RBF, and it couples them with Interface Quasi-Newton algorithms that accelerate the convergence. Its API is being used in a variety of well-known or in-house solvers, while official, user-ready adapters are provided for open-source packages such as OpenFOAM. The official OpenFOAM adapter supports conjugate heat transfer and fluid-structure interaction out-of-the box, while it was recently extended to also support fluid-fluid coupling.
This talk will present the current status of the coupling library preCICE and its OpenFOAM adapter to the OpenFOAM community, and it will discuss our current research into fluid-fluid coupling and geometric multiscale coupling.