Using virtual topology operations to generate analysis topology

Abstract

Virtual topology operations have been utilized to generate an analysis topology definition suitable for downstream mesh generation. Detailed descriptions are provided for virtual topology merge and split operations for all topological entities. Current virtual topology technology is extended to allow the virtual partitioning of volume cells and the topological queries required to carry out each operation are provided. Virtual representations are robustly linked to the underlying geometric definition through an analysis topology. The analysis topology and all associated virtual and topological dependencies are automatically updated after each virtual operation, providing the link to the underlying CAD geometry. Therefore, a valid description of the analysis topology, including relative orientations, is maintained. This enables downstream operations, such as the merging or partitioning of virtual entities, and interrogations, such as determining if a specific meshing strategy can be applied to the virtual volume cells, to be performed on the analysis topology description. As the virtual representation is a non-manifold description of the sub-divided domain the interfaces between cells are recorded automatically. This enables the advantages of non-manifold modelling to be exploited within the manifold modelling environment of a major commercial CAD system, without any adaptation of the underlying CAD model. A hierarchical virtual structure is maintained where virtual entities are merged or partitioned. This has a major benefit over existing solutions as the virtual dependencies are stored in an open and accessible manner, providing the analyst with the freedom to create, modify and edit the analysis topology in any preferred sequence, whilst the original CAD geometry is not disturbed. Robust definitions of the topological and virtual dependencies enable the same virtual topology definitions to be accessed, interrogated and manipulated within multiple different CAD packages and linked to the underlying geometry.

Automated Mesh Deformation for Computer-Aided Design Models That Exhibit Boundary Topology Changes

“…The key aspects of the technology is that it defines a new topology for a model without modifying the underlying BREP. It was described in [25] how the goal is to create a fit-for-purpose analysis topology, which is a description of topology unchanged. The key process used in this work is to apply virtual topology operations to merge groups of adjacent faces, creating virtual superset entities.…”

“…2. Note that this database builds on the work in [25], which is why in this work color is added as a new relation rather than as an additional attribute in the entity table.…”

Decomposing complex thin-walled CAD models for hexahedral-dominant meshing

“…Virtual Topology allows changes to be performed at a topological level without any modification of the underlying geometry. If the virtual topology technique is used, it is possible to achieve a virtual decomposition [30], where the underlying geometry is unchanged and the pitfalls associated with the direct geometry editing are avoided. For example, sliver regions generated from geometric tolerance issues are completely avoided as no complex surface intersections are required.…”

Data re-use for preliminary thermal-mechanical design of gas turbine engines

“…Another attractive solution to address the missing link between the geometry and its simulation models is through the Virtual Topology (VT) technology (23,24) . This concept has then been significantly developed and advanced by Armstrong et al (1,(25)(26)(27) . The idea of VT is to keep a virtual analysis model topology (the fidelity of which can vary during the design course) along with, but independent from, the actual geometry topology itself.…”

“…In a conventional iterative design cycle, on the one hand, the LOD process produces a simplified CAD model for the CAE process, where some geometric details (such as small-sized holes or fillets) are removed to reduce the mesh size. On the other hand, the LOA process is required when a more detailed analysis is to be produced (e.g., study the impact of the additional fillet features to the stress analysis) (1)(2)(3)20,26,27,33) . To achieve design fidelity and resolution changes, the conventional approaches are usually cumbersome and labour-intensive, and often require considerable engineering expertise.…”