Generic Volume Element Meshing for Optimization Applications

Abstract

In this paper the development of a FEM geometric preprocessor is described for use in a Design and Engineering Engine (DEE) for wing design, analysis and optimization in the conceptual design phase. The preprocessor of this DEE has been developed as Knowledge Based Engineering application using the ICAD Development Environment of Knowledge Technologies International (KTI). The preprocessor generates a volume mesh for parametric models which can be subsequently analysed with COTS or tailor made FE-packages and automatically updated by an optimizer. A single high order element type has been used to solve both the consistency and the convergency problem connected to FE-analysis in MDO environments. The pre-processor performance has been evaluated for parametric wing box structures defined in ICAD. MSC/Nastran has been used to evaluate performance of the tool. Modal analysis with the p-elements show that with a limited amount of pelements results comparable to shell elements are obtained. This means that this approach can solve both the convergence and the consistency problems related to automated meshing in MDO environments. Design and Engineering Engines To be able to analyse the application of new materials and structural concepts in aircraft wings, computer based design tools can be very effective. In this section the principle of Design and Engineering Engines (DEEs) for use in the conceptual design phase of aircraft wings is explained. The DEE principle can not only be used on product scale but also on other levels of the design cube, Fig.1, like quantum level, nano-level, micro-level, mesolevel and macro-level. A schematic outline of a DEE is shown in Fig.2. The DEE consists of a set of properly interconnected toolboxes such that automated multidisciplinary design, analysis and optimisation becomes feasible. The toolboxes are of different nature and include different pieces of analysis software, interface blocks etc. Core element of the DEE is a (multi-) model generator in which the parametrical description of the product resides. It gets input (a parameter set) from a concept/variant generator and generates/regenerates different models (aerodynamic, structural, costs etc) for the analysis tools (the discipline silos). The models consist of geometrical surfaces, numerical values, ASCII files etc. to feed the different analysis boxes (FEM packages, CFD codes etc). The output generated by the analysis tools is given back to an evaluator/ optimiser that on the basis of some target function gives a response and issues a new set of input data for the model generator. This new input for the model generator can be fed through the concept generator, whenever a different structural concept or even a different aircraft configuration is needed for the next iteration step. The general architecture of the DEE and the design of the single toolboxes need to be flexible to handle a wide range of different design problems with a minimum of modification required. No built-in design decisions in general should be hard-coded inside the toolboxes. The DEE is not intended to replace the functionality of property software tools (PATRAN, FLUENT, in-house developed tools etc), but to integrate them in a wider organised system. The multi-model generator should CONVERGER