HyperMesh in the Altair HyperWorks Platform is a powerful tool for geometric clean-up of high-frequency simulation models for Feko.
Altair EmployeeModel preprocessing for Feko HF-Simulation in HyperMesh
The Altair HyperWorks design and simulation platform empowers engineers to tackle physics simulation and concept design challenges across multiple disciplines for structures, motion, fluids, thermal, electromagnetics, electronics, controls, and embedded systems.
EM simulation models require a mesh, that needs to be created on the CAD geometry. Dependent on the solution method and object type line segments, triangles, tetrahedra or voxels can be used. The element size depends for most solvers on the simulation frequency, resp. the wavelength l. E.g. for metallic triangle elements the edge length should be in the range between l/8 and l/16. Dielectric regions could be modeled with surface triangles (using the so-called surface equivalence principle SEP) or with volume element (FEM-tetrahedra). For the classical full wave EM solvers MoM and MLFMM the elements are used to define piecewise-linear basis functions for the current distribution at the domain.
Here we would like to show how the EM simulation tool Feko and the Preprocessing tool HyperMesh (both available in the HyperWorks platform) can be combined to build fast workflows and to create appropriate meshes for high-frequency electromagnetic field simulations.
The CADFEKO tool has its own preprocessing functionality to build, import and mesh geometry. In many use cases the mesh can be automatically created with the Feko automesh functionality and the reader may ask, why another preprocessor should be used? Therefore, we will first classify a few preprocessing use cases when it makes sense to use HyperMesh (HM) instead of CADFEKO.
- Large CAD Geometry that needs a lot of clean up and mid-surface generation: For complex CAD data like full vehicle models the stronger cleaning functionality in HyperMesh pays off. E.g. automatic midsurface generation is powerful in HM and not available in CADFEKO.
- Sharing mesh models between different disciplines: When a model for different CAE disciplines needs to be build up, some tasks of the modelling and meshing effort can be leveraged and it makes sense to build the model for EM and e.g. structural simulation in the same tool HM, maybe even from the same HM expert user.
- Parametrizing meshes with morphing technology: For Optimization parametric models are required. For very complex models usually CAD parametrizations are not available anymore. But instead of the geometry the mesh can be parameterized using Morphing technology in HM.
Conversely, it can be said that for simpler models such as typical antennas, parameterization in CADFEKO is relatively easier to create. Especially for self-built models in CADFEKO (not imported from elsewhere) automeshing will be the best option. We therefore recommend using CADFEKO and not HM for antenna optimization at component level.
This article will provide only a brief overview on HM. More details on some useful HyperMesh tools and capabilities are shown in a video series in the Altair How-To Youtube channel (Video Series: HyperMesh for Feko Users). In 8 comprehensive sessions the different workflows and options are explained step by step. And for more advanced information HyperMesh training and resources are available on https://learn.altair.com/.
Tool Interface, Model Organization and Shape Recognition
The interface between Feko and HyperMesh with the fhm-file format enables the user to exchange complex models (including material properties) between both tools. This enables workflows that combine the strengths of both tools. Video 1 explains the interface and some basic information for users who may not be familiar with HyperMesh. In Video 2 the model organization options are described. This is important to assemble large, complex models efficiently and consistently by utilizing parts for subsystem level representations. One example of where such model management options are very helpful is the assignment of identical material parameters to special types of model parts.
In the recent HyperMesh 2023 release the AI-powered preprocessing tool ShapeAI has been added. Automated pattern and shape recognition capabilities let users select and edit similar shapes simultaneously. This reduces the need to model numerous individual parts and with advanced clustering technology and automatic feature extraction capabilities, users can speed-up the design process.
Clean-up and Creation of new Geometry
Imported CAD data is rarely clean. HyperMesh provides powerful features to repair and clean-up CAD structures in preparation for electromagnetic analysis. In order to prepare a structure for electromagnetic scattering analysis, for example, the connection of metallic parts must be correctly captured in the simulation model. If this connectivity is not correctly modeled, the current distribution computed on the object will not represent the actual current distribution (resonances may be missed or extra resonances added), resulting in a huge impact on the scattering analysis result. The connections between faces can be configured and visualized (using different colors) easily in HyperMesh.
Video 3 describes the manual workflow for Geometry clean-up while Video 4 shows the same functionality in a fully automated process.
For some situations, it could be necessary to create additional geometry to a simulation model. This is explained in Video 5.
Meshing and Morphing
Key features of HyperMesh are powerful tools for meshing of complex geometries with advanced tools and workflows for surface and solid meshing, such as mid-surface extraction, mid-meshing, and tetrahedral meshing. A demo of these workflows can be found in Video 6. This video also covers mesh quality evaluation and shows advanced mesh editing functionality.
To consider variations in the shape of a complex structure the morphing technology in HyperMesh is very powerful. In Video 7 you can watch how to morph a defined set of nodes using handles, anchors and geometric operations. Such deformations can be saved as so-called Shapes in HyperMesh. As Shapes are associated with design variables describing the amplitude of the deformation, shape optimization is possible using this approach.
In the final Video 8 model checks, Boolean operations on mesh level, and model export to Feko are explained. We hope that you enjoy this video series helping you to build efficient workflows for EM simulation preprocessing.