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

该项目的目标是开发一种优化的方法来模拟湍流中轻质柔性结构的瞬变流固相互作用。对于轻质结构的设计，与湍流的强相互作用是至关重要的。在第一阶段，考虑到两个领域的具体性质和特征尺度，开发和评估了一种基于两个学科的成熟求解器和一个耦合接口的专用分区FSI模拟方法。主要成果如下：1.涡旋分解法(LES)与薄壁柔性结构的一种稳健、高效、有效的耦合方法。2.应用IGA和精确耦合层ECL，大大改进了几何和运动学的建模(目前用于未修剪的NURBS曲面)。3.应用新开发的耦合软件Emire进行基于NURBS的几何造型。4.首次将新的FSI模拟方法应用于充气膜结构。最后的目标是：在流体方面，涡旋解析格式和直接连接的FSI耦合算法必须在两个方面得到进一步的发展：对于数值/方法问题，必须开发适当的网格变形算法，以允许将界面处新获得的高网格质量的表面网格转移到CFD体积网格。然而，决定性的是要明确考虑额外的计算工作量，并考虑大涡模拟-FSI耦合方法的特殊要求。关于物理/方法问题，迫切需要对湍流流入条件进行切合实际的描述。然而，由于轻质结构主要由零星出现的强风来加载，因此将开发一种湍流流入发生器，以考虑这种高度动态的载荷场景。在结构方面，主要重点是针对实际相关情况的面片和表面耦合方法的进一步发展，这些实际情况是由CAD生成的修剪多面片几何图形。目标是提供适当的几何和运动学公式，该公式在修剪的面片和面片界面(修剪的、未修剪的等)上也具有适当的几何曲面属性。满足了超细LES网格的高分辨率要求。进一步发展了两种策略：(1)FVM求解器与等几何结构模型的直接表面耦合；(2)与任意结构模型的耦合，例如使用ECL作为介质层的具有较低连续性的经典有限元模型。基于这一整个方法，将考虑对暴露在包括强风在内的湍流中的现实柔性结构的详细模拟和分析。

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.