College of Graduate Studies: Theses & Dissertations

Term of Award

Spring 2026

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Hossain Ahmed

Committee Member 1

Sevki Cesmeci

Committee Member 2

David Calamas

Abstract

Topologically protected wave propagation (TPWP) is a unique phenomenon in acoustic metamaterial, where tailored geometries and material properties enable controlled energy absorption and localizations. This study investigates TPWP through the systematic variation of unit cell geometry to capture multiple Dirac-like cone interactions within the Brillouin zone. While prior research had emphasized solid-solid interactions, the present work extends the framework by incorporating a solid-fluid configuration.

The primary objective of this study is to determine the influence of unit cell volume and material selection on  the formation of Dirac-like cones in the Brillouin zone, as well as on the corresponding bandgap characteristics. Specifically, the glue-based domain utilized in earlier studies is replaced with air, and the unit cell volume is reduced to examine whether previously observed behaviors persist across multiple parametric conditions. Eigenfrequency analyses are conducted using COMSOL Multiphysics to identify the conditions that promote TPWP. At a volume fraction of 0.4068, a Dirac-like cone was observed at 21.57 kHz, and TPWP characteristics were examined through detailed mode shape analysis. By increasing the number of unit cells in both the x and y directions, various array configurations, including rectangular, L-shaped, C-Shaped, and O-shape, were constructed to demonstrate topologically protected energy propagation using frequency-domain analysis. Spatial acoustic pressure distributions were evaluated across all array geometries to validate the presence of TPWP. For experimental validation, a rectangular array comprising a 10 × 5 grid of resonators was fabricated using an extrusion-based additive manufacturing process. Upon excitation by a pressure wave, acoustic pressure measurements were acquired at multiple locations along the array. The experimental observations exhibited close agreement with the numerical predictions, thereby confirming the TPWP phenomenon.

This work addresses a critical gap in acoustic metamaterials literature. Existing studies often draw analogies to Quantum Hall Effect or describe the TPWP phenomena as “Topological black holes” , despite the absence of magnetic fields in acoustic systems. Moving beyond such analogies, the present study systematically evaluates parametric variations within a solid–fluid unit cell, thereby establishing a physically realizable framework suitable for engineering applications. The contributions of this research are both theoretical and practical. Fundamentally, it advances the understanding of TPWP by clarifying the roles of unit cell volume and material domains in governing  the bandgap formation associated with Dirac-like cones. Practically, it provides design-oriented guidelines for leveraging TPWP in engineered systems for efficient energy localization and trapping.

OCLC Number

1592135743

Research Data and Supplementary Material

Yes

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