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Proceedings of CAD'17, 2017, 415-419
NURBS-based and Parametric-based Shape Optimisation with Differentiated CAD Kernel
Abstract. In engineering workflows it is common practice to maintain master CAD geometries, which then serve as a foundation for further design and development. Preserving CAD parametrisations during aerodynamic shape optimisation becomes challenging since existing CAD tools do not provide derivatives necessary for gradient-based design methods. Hence, gradients are obtained by approximations or with simplifications, precluding full CAD integration into the design optimisation loop. CAD-based methods allow simple and natural definition of geometrical constraints yielded by industry as well as streamline process while optimised shape exist in a CAD format. In the present work, we obtain exact CAD sensitivities (derivatives) with respect to CAD design parametrisation using our algorithmically differentiated Open Cascade Technology (OCCT) CAD-kernel software. The extension of this software for optimisation of parametric models and BRep (NURBS) compose the tool for explorations of the optimal shape in different by size and nature design spaces. In addition, we demonstrate the imposition of geometric constraints for both approaches, a salient part of industrial design, and an intuitive method of storing them in standard CAD format.
Keywords. Aerodynamic Shape Optimisation, CAD-based Optimisation, CAD sensitivities