An Interactive Preliminary Design System of High Speed Forebody and Inlet Flows

This paper demonstrates a simulation-based aerodynamic design process of high speed inlet. A genetic algorithm is integrated into the design process to facilitate the single objective optimization. The objective function is the total pressure recovery and is obtained by using a PNS solver for its computing efficiency. The system developed uses existing software of geometry definition, mesh generation and CFD analysis. The process which produces increasingly desirable design in each genetic evolution over many generations is automatically carried out. A generic two-dimensional inlet is created as a showcase to demonstrate the capabilities of this tool. A parameterized study of geometric shape and size of the showcase is also presented

Nonlinear analysis of composite shells with application to glass structures

Laminated glass is a special composite material, which is characterised by an alternating stiff/soft lay-up owing to the significant stiffness mismatch between glass and PVB. This work is motivated by the need for an efficient and accurate nonlinear model for the analysis of laminated glass structures, which describes well the through-thickness variation of displacement fields and the transverse shear strains and enables large displacement analysis. An efficient lamination model is proposed for the analysis of laminated composites with an alternating stiff/soft lay-up, where the zigzag variation of planar displacements is taken into account by adding to the Reissner-Mindlin formulation a specific set of zigzag functions. Furthermore, a piecewise linear through-thickness distribution of the material transverse shear strain is assumed, which agrees well with the real distribution, yet it avoids layer coupling by not imposing continuity constraints on transverse shear stresses. Local formulations of curved multi-layer shell elements are established employing the proposed lamination model, which are framed within local co-rotational systems to allow large displacement analysis for small-strain problems. In order to eliminate the locking phenomenon for the shell elements, an assumed strain method is employed and improved, which readily addresses shear locking, membrane locking, and distortion locking for each constitutive layer. Furthermore, a local shell system is proposed for the direct definition of the additional zigzag displacement fields and associated parameters, which allows the additional displacement variables to be coupled directly between adjacent elements without being subject to the large displacement co-rotational transformations. The developed multi-layer shell elements are employed in this work for typical laminated glass problems, including double glazing systems for which a novel volume-pressure control algorithm is proposed. Several case studies are finally presented to illustrate the effectiveness and efficiency of the proposed modelling approach for the nonlinear analysis of glass structures.Open Acces

Limit-point buckling analyses using solid, shell and solid–shell elements

In this paper, the recently-developed solid-shell element SHB8PS is used for the analysis of a representative set of popular limit-point buckling benchmark problems. For this purpose, the element has been implemented in Abaqus/Standard finite element software and the modified Riks method was employed as an efficient path-following strategy. For the. benchmark problems tested, the new element shows better performance compared to solid elements and often performs as well as state-of-the-art shell elements. In contrast to shell elements, it allows for the accurate prescription of boundary conditions as applied to the actual edges of the structure.Agence Nationale de la Recherche, France (ANR-005-RNMP-007

Randomized Computations for Efficient and Robust Finite Element Domain Decomposition Methods in Electromagnetics

Numerical modeling of electromagnetic (EM) phenomenon has proved to become an effective and efficient tool in design and optimization of modern electronic devices, integrated circuits (IC) and RF systems. However the generality, efficiency and reliability/resilience of the computational EM solver is often criticised due to the fact that the underlying characteristics of the simulated problems are usually different, which makes the development of a general, \u27\u27black-box\u27\u27 EM solver to be a difficult task. In this work, we aim to propose a reliable/resilient, scalable and efficient finite elements based domain decomposition method (FE-DDM) as a general CEM solver to tackle such ultimate CEM problems to some extent. We recognize the rank deficiency property of the Dirichlet-to-Neumann (DtN) operators involved in the previously proposed FETI-2$\lambda$ DDM formulation and apply such principle to improve the computational efficiency and robustness of FETI-2$\lambda$ DDM. Specifically, the rank deficient DtN operator is computed by a randomized computation method that was originally proposed to approximate matrix singular value decomposition (SVD). Numerical results show a up to 35\% run-time and 75% memory saving of the DtN operators computation can be achieved on a realistic example. Later, such rank deficiency principle is incorporated into a new global DDM preconditioner (W-FETI) that is inspired by the matrix Woodbury identity. Numerical study of the eigenspectrum shows the validity of the proposed W-FETI global preconditioner. Several industrial-scaled examples show significant iterative convergence advantage of W-FETI that uses 35%-80% matrix-vector-products (MxVs) than state-of-the-art DDM solvers

Developments on Shell and Solid-Shell finite elements technology in nonlinear continuum mechanics

Tese de mestrado. Faculdade de Engenharia. Universidade do Porto. 199