Parametric Geometry Model Research Articles

Transonic Airfoil Shape Optimization in Preliminary Design Environment

A modified profile optimization method using a smoothest shape modification strategy (POSSEM) is developed for airfoil shape optimization in a preliminary design environment. POSSEM is formulated to overcome two technical diculties frequently encountered when conducting multipoint airfoil optimization within a high-resolution design space: the generation of undesirable optimal airfoil shapes due to high frequency components in the parametric geometry model and significant degradation in the o-design performance. To demonstrate the usefulness of POSSEM in a preliminary design environment, a design competition was conducted with the objective of improving a fairly well-designed baseline airfoil at four transonic flight conditions without incurring any o-design performance degradation. Independently, two designs were generated from the inverse design tool CDISC, while a third design was generated from POSSEM using over 200 control points of a cubic B-spline curve representation of the airfoil as design variables for the shape optimization. Pros and cons of all the airfoil designs are documented along with in-depth analyses of simulation results. The POSSEM design exhibits a fairly smooth curvature and no degradation in the o-design performance. Moreover, it has the lowest average drag among the three designs at the design conditions, as evaluated from three dierent flow solvers. This study demonstrates the potential of POSSEM as a practical airfoil optimization tool for use in a preliminary design environment. The novel ideas used in POSSEM, such as the smoothest shape modification and modified profile optimization strategies, are applicable to minimizing aircraft drag at multiple flight conditions.

Supervised Learning Approach to Parametric Computer-Aided Design Geometry Repair

Multidisciplinary optimization systems rely increasingly on parametric CAD engines to supply the geometries required by their analysis components. Such parametric geometry models usually result from an uneasy compromise between high flexibility, that is, the ability to morph into a wide variety of topologies and shapes, and robustness, the ability to produce feasible, sensible topologies and shapes throughout most of the design space. It is argued that a possible means of achieving both objectives is via a supervised learning system attached to the CAD model. It is shown that such a model can capture some of the engineering and geometrical judgment of the designer and can thereafter be used to repair design variable sets that lead to infeasible CAD models.

Solving CSG equations for checking equivalency between two different geometric models

For two given parametric constructive solid geometry (CSG) models, the problem of determining their parameter domains in which the two models are equivalent is addressed. Here, two CSG models are equivalent if they represent the exact same region in R 3, although their constituent features and feature attributes may differ. In this paper, an approach for solving the problem in a limited scope is proposed, in which a CSG model is polyhedral, its parametric form is explicit and its feature orientations are fixed. The solution includes the equivalent parameter domain for each model and parameter mapping that associates these two models on their equivalent parameter domains. One application of this research is to identify the equivalent parameter domains of two parametric part models, respectively, in the design option space and in the capability envelope set of a parametric machining process in order to facilitate the interoperation between part design and process planning through the generated parameter mapping between these two different kinds of models.

Shape optimization of GIS insulator barrier

A gas insulated substation (GIS) barrier with conical insulators from a cast epoxy resin is optimized to withstand AC and DC stresses. The field distribution across insulators with long creepage path and field distortion due to the deposition of charge on the insulator surface is calculated on a parametric geometry model by finite element techniques. The shape of the insulator and surrounding electrodes was improved fairly quickly using a direct search method with constraints. The results of optimization were verified by standard measurements on high voltage insulators in SF6 gas.