Shape optimization directly from CAD: an isogeometric boundary element approach

The present thesis addresses shape sensitivity analysis and optimization in linear elasticity with the isogeometric boundary element method (IGABEM), where the basis functions used for constructing geometric models in computer-aided design (CAD) are also employed to discretize the boundary integral equation (BIE) for structural analysis, and to discretize the material differentiation form of the BIE for shape sensitivity analysis. To guarantee water-tight and locally-refined geometries, we use non-uniform rational B-splines (NURBS) and T-splines for two-dimensional and three dimensional problems, respectively. In addition, we take advantage of the regularized form of BIE instead of the singular form, to bypass the difficulties caused by the evaluation of strongly singular integrals and jump terms. The main advantages of the present work arise from the ability of the IGABEM to seamlessly integrate CAD and numerical analysis, since they share the same boundary representation of geometric models. Therefore, throughout the whole shape optimization, it does not need a costly meshing/remeshing procedure. Moreover, the control points can be naturally chosen as the design variables, and the optimal solution can be directly returned to the CAD system without any smoothing procedure

Compressed air energy storage: characteristics, basic principles, and geological considerations

With increasing global energy demand and increasing energy production from renewable resources, energy storage has been considered crucial in conducting energy management and ensuring the stability and reliability of the power network. By comparing different possible technologies for energy storage, Compressed Air Energy Storage (CAES) is recognized as one of the most effective and economical technologies to conduct long-term, large-scale energy storage. In terms of choosing underground formations for constructing CAES reservoirs, salt rock formations are the most suitable for building caverns to conduct long-term and large-scale energy storage. The existing CAES plants and those under planning have demonstrated the importance of CAES technology development. In both Canada and China, CAES plants are needed to conduct renewable energy storage and electricity management in particular areas. Although further research still needs to be conducted, it is feasible and economical to develop salt caverns for CAES in Canada and China.Cited as: Li, L., Liang, W., Lian, H., Yang, J., Dusseault, M. Compressed air energy storage: characteristics, basic principles, and geological considerations. Advances in Geo-Energy Research, 2018, 2(2): 135-147, doi: 10.26804/ager.2018.02.0

ADVANCES IN GEOMETRY INDEPENDENT APPROXIMATIONS

We present recent advances in geometry independent field approximations. The GIFT approach is a generalisation of isogeometric analysis where the approximation used to describe the field variables no-longer has to be identical to the approximation used to describe the geometry of the domain. As such, the geometry can be described using usual CAD representations, e.g. NURBS, which are the most common in the CAD area, whilst local refinement and meshes approximations can be used to describe the field variables, enabling local adaptivity. We show in which cases the approach passes the patch test and present applications to various mechanics, fracture and multi-physics problems