Otimização topológica evolucionária de problemas com interação fluido-estrutura

Orientador: Renato PavanelloTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: O objetivo desta tese é o desenvolvimento de uma ferramenta computacional para projeto de estruturas considerando interação fluido-estrutura usando otimização topológica. Uma metodologia de otimização estrutural topológica é proposta associada à formulações de elementos finitos em problemas fluido-estrutura acoplados. Nesses tipos de problemas a estrutura sofre carregamentos advindos do meio fluido, ou seja, pressão e/ou forças viscosas. As dificuldades em se projetar estruturas sob carregamentos de fluidos surgem devido à variação da localização, direção e magnitude dos carregamentos quando a forma e topologia da estrutura são alteradas durante a otimização. Isso se torna o principal desafio para os métodos tradicionais baseados na interpolação da densidade do material. Nesses métodos, as superfícies em contato com o fluido não são definidas explicitamente devido à existência de elementos estruturais de densidade intermediária. Neste trabalho é proposta uma metodologia alternativa para esse tipo de carregamento dependente da topologia. Com a extensão do método de otimização estrutural evolucionária bidirecional (BESO) associada à formulações fluido-estrutura acopladas, pressões e forças viscosas podem ser modeladas diretamente para qualquer topologia estrutural devido à natureza discreta dos métodos evolucionários. Assim, o problema é resolvido sem a necessidade de parametrização das superfícies de carregamentos de pressão. A metodologia BESO é estendida considerando os procedimentos de alteração entre elementos fluido-estrutura-vazios, novas análises de sensibilidade e restrições. Problemas em estado estacionário são considerados, incluindo elasticidade linear para a análise estrutural e as equações de Laplace, Helmholtz e escoamento incompressível de Navier-Stokes para a análise do fluido. Carregamentos constantes e não constantes são modelados. Diversos exemplos e aplicações são explorados com a metodologia propostaAbstract: The aim of this thesis is the development of a computational tool for the design of structures considering fluid-structure interaction using topology optimization. A methodology of structural topology optimization is proposed in association with finite element formulations of fluid-structure coupled problems. In this type of problems, the structure undergoes fluid loading, i.e., pressure and/or viscous loads. The difficulties in designing fluid loaded structures arise due to the variation of location, direction and magnitude of the loads when the structural shape and topology change along the optimization procedure. This turns out to be an additional difficulty for the traditional density-based topology optimization methods. In density-based methods, the pressure loaded surfaces are not explicitly defined due to the existence of intermediate density elements. In this thesis, it is suggested an alternative methodology to handle this type of design-dependent loads. With an extended bi-directional evolutionary structural optimization (BESO) method associated with different fluid-structure formulations, pressures and viscous loads can be modelled straightforwardly for any structural topology due to the discrete nature of the method. Thus, the problem is solved without any need for pressure load surfaces parametrization. The BESO methodology is extended considering the procedures of switching fluid-structure-void elements, new sensitivity analyses and constraints. Steady state problems are considered, including linear elasticity for the structural analysis and Laplace, Helmholtz and incompressible Navier-tokes flow equations for the fluid analysis. Constant and non constant loads are modelled. Several examples and applications are explored with the proposed methodologyDoutoradoMecanica dos Sólidos e Projeto MecanicoDoutor em Engenharia Mecânica2011/09730-6FAPES

A stable and accurate control-volume technique based on integrated radial basis function networks for fluid-flow problems

Radial basis function networks (RBFNs) have been widely used in solving partial differential equations as they are able to provide fast convergence. Integrated RBFNs have the ability to avoid the problem of reduced convergence-rate caused by differentiation. This paper is concerned with the use of integrated RBFNs in the context of control-volume discretisations for the simulation of fluid-flow problems. Special attention is given to (i) the development of a stable high-order upwind scheme for the convection term and (ii) the development of a local high-order approximation scheme for the diffusion term. Benchmark problems including the lid-driven triangular-cavity flow are employed to validate the present technique. Accurate results at high values of the Reynolds number are obtained using relatively-coarse grids

Layout optimization for multi-bi-modulus materials system under multiple load cases

Financial support from the National Natural Science Foundation of China (Grant No. 51179164) and the Australian Research Council (Grant No. DP140103137) is acknowledged

Singing synthesis with an evolved physical model

A two-dimensional physical model of the human vocal tract is described. Such a system promises increased realism and control in the synthesis. of both speech and singing. However, the parameters describing the shape of the vocal tract while in use are not easily obtained, even using medical imaging techniques, so instead a genetic algorithm (GA) is applied to the model to find an appropriate configuration. Realistic sounds are produced by this method. Analysis of these, and the reliability of the technique (convergence properties) is provided

A fast topology optimization method of damping material layer for noise reduction to elastic curved plate-cavity structure

This paper presents a fast topology optimization method of damping material layer for noise reduction to elastic curved plate (shell)-cavity structure. Using less as far as possible the damping materials reach the maximum efficiency of one's vibration or noise reduction. Energy method is employed. The way to determine the location where the damping material pasted on is to find the location where damping material’s energy will lose more. The computational model is based on a finite element discretization. Assuming pasting a small amount of damping materials on the structure has little effect on vibration mode, the relationship between energy loss of the damping material on each element and the displacement of the nodes of the plate (shell) during a period of vibration was deduced. Damping material was laid out on the element location where damping layer energy will lose most, and then the second gradually, until optimization target was achieved. Commercial finite element software was used to obtain the finite element model of complex engineering structures. Nodes information, stiffness and mass matrix were read out by Matlab subroutines. A numerical result of topology optimization of damping material layer on the curved plate-cavity structure noise reduction was presented. The topology optimization method is approximate, simple and suitable for complex engineering applications

Topology Optimization Applications on Engineering Structures

Over the years, several optimization techniques were widely used to find the optimum shape and size of engineering structures (trusses, frames, etc.) under different constraints (stress, displacement, buckling instability, kinematic stability, and natural frequency). But, most of them require continuous data set where, on the other hand, topology optimization (TO) can handle also discrete ones. Topology optimization has also allowed radical changes in geometry which concludes better designs. So, many researchers have studied on topology optimization by developing/using different methodologies. This study aims to classify these studies considering used methods and present new emerging application areas. It is believed that researchers will easily find the related studies with their work

Topology and shape optimization of dissipative and hybrid mufflers

[EN] This article presents a Topology Optimization (TO) method developed for maximizing the acoustic attenuation of a perforated dissipative muffler in the targeted frequency range by optimally distributing the absorbent material within the chamber. The Finite Element Method (FEM) is applied to the wave equation formulated in terms of acoustic pressure (chamber) and velocity potential (central duct, due to the existence of thermal gradients and mean flow) in order to evaluate the acoustic performance of the noise control device in terms of Transmission Loss (TL). Sound propagation through the chamber fibrous material is modelled considering complex equivalent acoustic properties, which vary spatially not only as a function of temperature, but also as a function of the lling density, since non-homogeneous density distributions are considered. The acoustic coupling at the perforated duct is performed by introducing a coordinate-dependent equivalent impedance. The objective function to maximize is expressed as the mean TL in the targeted frequency range. The sensitivities of this function with respect to the filling density of each element in the chamber are evaluated following the standard adjoint method. The Method of Moving Asymptotes (MMA) is used to update the design variables at each iteration of the TO process, keeping the weight of absorbent material equal or lower than a given value, while maximizing attenuation. Additionally, several particular designs inferred from the topology optimization results are analyzed. For example, the sizing optimization of a number of rings is carried out simultaneously with the aforementioned TO process (density layout). A reactive chamber is added in order to evaluate the TL of a hybrid muffler and its shape optimization is also carried out simultaneously with the aforementioned TO. 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