An Investigation on Acoustic Metamaterial Physics to Inspire the Design of Novel Aircraft Engine Liners

Attenuation of low frequency turbofan engine noise has been a challenging task in an industry that requires low weight and tightly-packed solutions. Without innovative advancements, the technology currently used will not be able to keep up with the increasingly stringent requirements on aircraft noise reduction. A need exists for novel technologies that will pave the way for the future of quiet aircraft. This thesis investigates acoustic metamaterials and their ability to achieve superior transmission loss characteristics not found in traditional honeycomb liners. The acoustic metamaterials investigated are an array of Helmholtz resonators with and without coupled cavities periodically-spaced along a duct wall. Analytical, numerical, and experimental developments of these acoustic metamaterial systems are used herein to study the effects of this technology on the transmission loss. Particularly focusing on analytical modeling will aid in understanding the underlying physics that governs their interesting transmission loss behavior. A deeper understanding of the physics will be used to aid in future acoustic metamaterial liner design. A parameter study is performed to understand the effects of the geometry, spacing, and number of resonators, as well as resonator cavity coupling on performance. Increased broadband transmission loss, particularly in low frequencies, is achieved through intelligent manipulation of these parameters. Acoustic metamaterials are shown to have appealing noise cancellation characteristics that prove to be effective for aircraft engine liner applications.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Mechanical Engineering

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2024

Author dc:creator

• Hubinger, Benjamin Evan

Chair dc:contributor.committeechair

• Fuller, Christopher R.

Committee members dc:contributor.committeemember

• Southward, Steve C.
• Tian, Zhenhua
• Nark, Doug

• Acoustic Meta Materials (AMM)
• Turbofan Engine
• Helmholtz Resonator
• Transfer Matrix Method (TMM)
• Bloch Wave Theory

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:38693

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/118609