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Shape optimisation with multiresolution subdivision surfaces and immersed finite elements


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Authors

Bandara, K 
Rüberg, T 

Abstract

We develop a new optimisation technique that combines multiresolution subdivision surfaces for boundary description with immersed finite elements for the discretisation of the primal and adjoint problems of optimisation. Similar to wavelets multiresolution surfaces represent the domain boundary using a coarse control mesh and a sequence of detail vectors. Based on the multiresolution decomposition efficient and fast algorithms are available for reconstructing control meshes of varying fineness. During shape optimisation the vertex coordinates of control meshes are updated using the computed shape gradient information. By virtue of the multiresolution editing semantics, updating the coarse control mesh vertex coordinates leads to large-scale geometry changes and, conversely, updating the fine control mesh coordinates leads to small-scale geometry changes. In our computations we start by optimising the coarsest control mesh and refine it each time the cost function reaches a minimum. This approach effectively prevents the appearance of non-physical boundary geometry oscillations and control mesh pathologies, like inverted elements. Independent of the fineness of the control mesh used for optimisation, on the immersed finite element grid the domain boundary is always represented with a relatively fine control mesh of fixed resolution. With the immersed finite element method there is no need to maintain an analysis suitable domain mesh. In some of the presented two- and three-dimensional elasticity examples the topology derivative is used for creating new holes inside the domain.

Description

Keywords

Shape optimisation, Immersed finite elements, Multiresolution surfaces, Subdivision schemes, Isogeometric analysis, Catmull-Clark

Journal Title

Computer Methods in Applied Mechanics and Engineering

Conference Name

Journal ISSN

0045-7825
1879-2138

Volume Title

300

Publisher

Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/G008531/1)
The partial support of the EPSRC through grant # EP/G008531/1 and EC through Marie Curie Actions (IAPP) program CASOPT project are gratefully acknowledged.