Eddy resolving simulation methodology for dynamic fluid-structure interactions of lightweight flexible surface structures

• Applicants: Professor Dr.-Ing. Kai-Uwe Bletzinger; Professor Dr.-Ing. Michael Breuer
• Subject Area: Fluid Mechanics ; Applied Mechanics, Statics and Dynamics
• Term: from 2012 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 211249184

The objective of the project is to develop an optimized methodology for the simulation of transient fluid-structure interactions oflightweight flexible structures in turbulent wind flow. For the design of lightweight structures, the strong interaction with the turbulenthighly vortical flow is crucial. In the first period a dedicated partitioned FSI simulation methodology based on well establishedsolvers for both disciplines and a coupling interface was developed and evaluated, taking the specific properties and the characteristic scales of both fields into account. The main achievements are:1. Robust, efficient and comprehensively validated coupling method between eddy-resolving methods (LES) and thin-walled flexiblestructures. 2. Strongly improved modeling of the geometry and the kinematics (presently for non-trimmed NURBS surfaces) applying IGA andan exact coupling layer ECL. 3. Application of the newly developed coupling software EMPIRE for a NURBS-based geometry modeling. 4. First application of the new FSI simulation methodology to an inflated membrane structure. In the continuation the final goal is pursued:On the fluid side the eddy-resolving scheme and the directly connected FSI coupling algorithm has to be developed further in two regards: With respect to numerical/methodical issues an appropriate grid deformation algorithm has to be developed, which allows to transfer the newly achieved high grid quality of the surface mesh at the interface to the CFD volume grid. However, it is decisive to take distinctly the additional computational effort into account and to also consider the special requirements of the coupled LES-FSImethodology. With respect to physical/methodical issues a realistic description of the turbulent inflow conditions is urgentlyrequired. However, since lightweight structures are mainly loaded by sporadically appearing strong wind gusts, a turbulence inflowgenerator will be developed which takes this highly dynamic load scenario into account.On the structural side the main focus lies on the further methodical developments of the patch and surface coupling methods forpractically relevant cases of trimmed multi-patch geometries generated by CAD. The goal is to provide an appropriate geometric and kinematic formulation which possesses suitable geometric surface properties also on trimmed patches and at patch interfaces (trimmed, non-trimmed, etc.) and fulfill the requirements of the high resolution of the very fine LES grids. Two strategies are further developed: (1) A direct surface coupling of the FVM-solver with the isogeometric structural model and (2) a coupling to arbitrary structural models such as classical FEM possessing lower continuity properties using ECL as a mediator layer.Based on this entire methodology, detailed simulations and analyses of realistic flexible structures exposed to turbulent wind flows including strong gusts will be considered.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Roland Wüchner