Topology Optimization for Wave Propagation Problems with Experimental Validation

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Abstract

This Thesis treats the development and experimental validation of density-based topology optimization methods for wave propagation problems. Problems in the frequency regime where design dimensions are between approximately one fourth and ten wavelengths are considered. All examples treat problems from acoustics, however problems for TE or TM polarized electromagnetic waves and shear waves in solids in two dimensions may be treated using the proposed methods with minor modifications.
A brief introduction to wave problems and to density-based topology optimizationis included, as is a brief discussion of the finite element method and a hybrid ofa wave based method and the finite element method, used to discretize the modelproblems under consideration.
A short discussion of the benefits and drawbacks of applying the hybrid method compared to the finite element method, used in conjunction with topology optimization, is included. Preliminary results for novel preconditioners used in conjunction with the generalized minimal residual method for the iterative solution of waveproblems, potentially suited for use with topology optimization, are discussed.
The development of an extension to an existing method, for assuring geometricrobustness of designs created using density-based topology optimization, is presented.The method is applied to acoustic cavity design, and a significant improvement inthe geometric robustness of several cavities demonstrated. Experimental validationof an acoustic cavity designed using the proposed method is provided.
A novel approach for designing meta material slabs with selectively tuned negative refractive behavior is outlined. Numerical examples demonstrating the behavior of a slab under different conditions is provided. Results from an experimental studydemonstrating agreement with numerical predictions are presented.
Finally an approach for designing acoustic wave shaping devices is treated. Three examples of applications are presented, a directional sound emission device, a wave splitting device and a flat focusing lens. Experimental results for the first two devices,demonstrating good agreement between measurements and the numerical predictions, are provided.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages167
ISBN (Electronic)978-87-7475-460-2
Publication statusPublished - 2016
SeriesDCAMM Special Report
NumberS208
ISSN0903-1685

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