European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS-2016)

Gugala, M

JESUDASAN, R

Mueller, J

Zhang, X

Queen Mary Research Online

ECCOMAS Congress 2016CAD-free vs CAD-based parametrisation method in adjoint based aerodynamicshape optimizationRejish Jesudasan1*, Xingchen Zhang1, Mateusz Gugala1, Jens-Dominik Mueller11QUEEN MARY UNIVERSITY OF LONDONMile End Rd, London E1 4NS{r.jesudasan,xingchen.zhang}@qmul.ac.uk ABSTRACTKey words: Parametrisation, CAD-based, Node-based, Adjoint, Shape optimisation. Adjoint based aerodynamic shape optimisation methods have recently become very popular in theaerospace, automotive and marine industries. The adjoint method is essential for gradient based optimi-sation with many design variables since the gradient of the objective function is computed at a cost thatis independent of the number of design variables. This method reduces the computational complexity insensitivity evaluation for each design variable. Various methods for parametrisation of the geometry havebeen proposed [1]. Two well-known 3D geometry parametrisation methodologies are focused upon hereas they offer rich design spaces: a) the CAD-free node based approach and b) the CAD-based NURBS.The CAD/NURBS approach [2] works with the generic boundary representation using NURBS patchesas typically given in the STEP file format. The control points and weights of the NURBS patches are usedas design variables, offering the richest design space the geometric representation can express. Additionalconstraints have to be introduced to maintain continuity between the patches, thickness, radius or boxconstraints during the optimisation.In the node-based parametrisation the positions of the grid nodes on the shape are taken as the designvariables. This is the richest design space the grid can express, and is typically too rich as it allows high-frequency oscillations that the flow solver does not adequately resolve, regularisation of the gradients orsmoothing of the shape is required.In this paper, the two approaches are discussed and compared using an in-house flow and adjoint solver.The test case is the minimisation of pressure loss of a 3-D S-Bend duct and the drag minimisation of anOnera M6 wing in transonic flight. Particular attention will be paid to comparisons of computational time,quality of the optima and their sensitivity to the choice of regularisation method and value, or constraintaccuracy parameters.Acknowledgement: This work is conducted with the IODA project funded by the European Union’sH2020 Programme under Grant Agreement No. 642959.References[1] J. A. Samareh, “Survey of shape Parameterization techniques for high-fidelity multidisciplinary shapeoptimization,” AIAA Journal, vol. 39, no. 5, pp. 877–884, May 2001.[2] S. Xu, W. Jahn, and J.-D. Müller, “CAD-based shape optimisation with CFD using a discrete adjoint,”International Journal for Numerical Methods in Fluids, vol. 74, no. 3, pp. 153–168, 2014. [Online]. Available:http://dx.doi.org/10.1002/fld.3844  Powered by TCPDF (www.tcpdf.org)                                              1 / 1

CAD-free vs CAD-based parametrisation method in adjoint-based​ aerodynamic shape optimization

https://qmro.qmul.ac.uk/xmlui/bitstream/123456789/16063/1/Jesudasan%20CAD-free%20abstract%202016%20Published.pdf

CAD-free vs CAD-based parametrisation method in adjoint-based aerodynamic shape optimization

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Queen Mary Research Online

CAD-free vs CAD-based parametrisation method in adjoint-based​ aerodynamic shape optimization

Abstract

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Queen Mary Research Online

CAD-free vs CAD-based parametrisation method in adjoint-based aerodynamic shape optimization