Geometry Fidelity Research Articles

Automatic surface repairing, defeaturing and meshing algorithms based on an extended B-rep

This paper presents an extended surface boundary representation (B-rep), where each topology entity can have dual geometric representations to accommodate various defects (e.g., gaps and overlaps) commonly present in CAD models. Keeping a uniform B-rep and the unsuppressed geometry data enables the use of various existing repairing, defeaturing and meshing algorithms to process CAD models with small gaps and overlaps on surface boundaries. The continuous geometry of the input model remains untouched in the repairing, defeaturing and meshing process, and the output mesh is loyal to this geometry. Such feature is often desirable in numerical simulations that require meshes with high geometry fidelity.

The Analysis of the Aerodynamic Character and Structural Response of Large-Scale Wind Turbine Blades

A process of detailed CFD and structural numerical simulations of the 1.5 MW horizontal axis wind turbine (HAWT) blade is present. The main goal is to help advance the use of computer-aided simulation methods in the field of design and development of HAWT-blades. After an in-depth study of the aerodynamic configuration and materials of the blade, 3-D mapping software is utilized to reconstruct the high fidelity geometry, and then the geometry is imported into CFD and structure finite element analysis (FEA) software for completely simulation calculation. This research process shows that the CFD results compare well with the professional wind turbine design and certification software, GH-Bladed. Also, the modal analysis with finite element method (FEM) predicts well compared with experiment tests on a stationary blade. For extreme wind loads case that by considering a 50-year extreme gust simulated in CFD are unidirectional coupled to the FE-model, the results indicate that the maximum deflection of the blade tip is less than the distance between the blade tip (the point of maximum deflection) and the tower, the material of the blade provides enough resistance to the peak stresses the occur at the conjunction of shear webs and center spar cap. Buckling analysis is also included in the study.

Flexible and robust CAD models for design automation

This paper explores novel methodologies for enabling Multidisciplinary Design Optimization (MDO) of complex engineering products. To realize MDO, Knowledge Based Engineering (KBE) is adopted with the aim of achieving design reuse and automation. The aim of the ongoing research at Linköping University is to shift from manual modeling of disposable geometries to Computer Aided Design (CAD) automation by introducing generic high level geometry templates. Instead of repeatedly modeling similar instances of objects, engineers should be able to create more general models that can represent entire classes of objects. The proposed methodology enables utilization of commercial design tools, hence taking industrial feasibility into consideration. The concept of High Level CAD templates (HLCt) will be proposed and discussed as the building blocks of flexible and robust CAD models, which in turn enables high fidelity geometry in the MDO loop. Furthermore, quantification of the terms flexibility and robustness are presented, providing a means to measure the quality of the geometry models. Finally, application examples are presented in which the outlined framework is evaluated. The applications have been chosen from three ongoing research projects aimed at automating the design of transport aircraft, industrial robots, and micro air vehicles.

Geometry and mesh generation for high fidelity computational simulations using non-uniform rational B-splines

High fidelity simulations using mesh-based computational technologies such as computational fluid dynamics and computational structural mechanics are very important in providing valuable performance information of a design. These simulations, however, require accurate geometry representation as well as high quality meshes about the design in order to obtain accurate data. Unfortunately, while three-dimensional complex geometry is involved, it is a challenge to maintain geometry fidelity while trying to obtain high quality meshes. This paper discusses detailed information associated with non-uniform rational B-splines (NURBS) and its utilizations for geometry and mesh generation. It will go beyond regular curve and surface formulations to include NURBS volume and dynamic NURBS. Detailed NURBS formulations are described through mathematical expressions and applications to demonstrate the versatility and reliability of NURBS in geometry and mesh generation that enable high performance computational simulations.