6 research outputs found
A semi-structured approach to curvilinear mesh generation around streamlined bodies
We present an approach for robust high-order mesh generation specially
tailored to streamlined bodies. The method is based on a semi-sructured
approach which combines the high quality of structured meshes in the near-field
with the flexibility of unstructured meshes in the far-field. We utilise medial
axis technology to robustly partition the near-field into blocks which can be
meshed coarsely with a linear swept mesher. A high-order mesh of the near-field
is then generated and split using an isoparametric approach which allows us to
obtain highly stretched elements aligned with the flow field. Special treatment
of the partition is performed on the wing root juntion and the trailing edge
--- into the wake --- to obtain an H-type mesh configuration with anisotropic
hexahedra ideal for the strong shear of high Reynolds number simulations. We
then proceed to discretise the far-field using traditional robust tetrahedral
meshing tools. This workflow is made possible by two sets of tools: CADfix,
focused on CAD system, the block partitioning of the near-field and the
generation of a linear mesh; and NekMesh, focused on the curving of the
high-order mesh and the generation of highly-stretched boundary layer elements.
We demonstrate this approach on a NACA0012 wing attached to a wall and show
that a gap between the wake partition and the wall can be inserted to remove
the dependency of the partitioning procedure on the local geometry.Comment: Preprint accepted to the 2019 AIAA Aerospace Sciences Meetin
Applying database optimization technologies to feature recognition in CAD
In engineering analysis, CAD models are often simplified by removing features, enabling meshing to be quicker and more reliable; the resulting smaller meshes in turn lead to faster analysis. Finding features by hand is tedious, and there is a need to automate this process. A declarative approach to feature recognition allows engineers to define features relevant to a particular problem, without detailing how they are to be found. Here, we show that a declarative feature definition can be turned into an SQL query, and database engine coupled to a CAD modeler can be used to find instances of entities satisfying the predicates which make up features. A key benefit of doing so is that database optimization techniques built into a modern database can effectively execute the SQL query in an acceptable time to find features. We present experiments to show the benefits of various database optimization techniques. We determine how the time taken to find features scales with number of features and model size, using different optimizations. We also give results for real industrial models