Abstract
Metamaterials are artificial media composed of subwavelength unit cells,
specifically engineered to exhibit unusual properties in relation to wave
propagation, generally not found in nature. Most research in this area has
been dedicated to electromagnetic metamaterials, In this thesis we present
results in a new multidisciplinary field of metamaterials in acoustics and
realization of non-conventional wave propagation applying novel
metamaterial unit cells. The scientific contribution of this dissertation
comprises three new types of wave propagation modes and their control with
newly designed metamaterial unit cells. In the thesis, a novel class of
compressibility-near-zero (CNZ) acoustic propagation, achieved by using
Helmholtz resonators, is theoretically analyzed and experimentally
demonstrated. A closed analytical formula for the effective compressibility of
the proposed unit cell is presented, and the existence of two frequencies
which may support CNZ propagation is shown. Furthermore, a new unit cell
with effective mass density with Lorentzian type behavior is proposed, a
closed analytical formula for its effective mass density is found, and the
evanescent, left-handed propagation and density-near-zero acoustic wave
propagation аre demonstrated. In the end it is demonstrated for the first time
that a surface acoustic wave propagating at the boundary between a fluid
and a hard grooved surface can be efficiently controlled by varying only the
temperature of the fluid, while the geometry of the grooved surface remains
unchanged. This opens up a way for a number of new applications, all easily
tunable by external means. Following theoretical considerations, we
demonstrate temperature-controlled sound trapping and its applications in
acoustic spectral analysis and temperature sensing. We also present a
temperature-controlled gradient refractive index (GRIN) acoustic medium and
apply it to achieve temperature-controlled acoustic focusing.
specifically engineered to exhibit unusual properties in relation to wave
propagation, generally not found in nature. Most research in this area has
been dedicated to electromagnetic metamaterials, In this thesis we present
results in a new multidisciplinary field of metamaterials in acoustics and
realization of non-conventional wave propagation applying novel
metamaterial unit cells. The scientific contribution of this dissertation
comprises three new types of wave propagation modes and their control with
newly designed metamaterial unit cells. In the thesis, a novel class of
compressibility-near-zero (CNZ) acoustic propagation, achieved by using
Helmholtz resonators, is theoretically analyzed and experimentally
demonstrated. A closed analytical formula for the effective compressibility of
the proposed unit cell is presented, and the existence of two frequencies
which may support CNZ propagation is shown. Furthermore, a new unit cell
with effective mass density with Lorentzian type behavior is proposed, a
closed analytical formula for its effective mass density is found, and the
evanescent, left-handed propagation and density-near-zero acoustic wave
propagation аre demonstrated. In the end it is demonstrated for the first time
that a surface acoustic wave propagating at the boundary between a fluid
and a hard grooved surface can be efficiently controlled by varying only the
temperature of the fluid, while the geometry of the grooved surface remains
unchanged. This opens up a way for a number of new applications, all easily
tunable by external means. Following theoretical considerations, we
demonstrate temperature-controlled sound trapping and its applications in
acoustic spectral analysis and temperature sensing. We also present a
temperature-controlled gradient refractive index (GRIN) acoustic medium and
apply it to achieve temperature-controlled acoustic focusing.
Original language | English |
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Qualification | Doctor of Philosophy |
Awarding Institution |
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Award date | 16 Dec 2015 |
Publication status | Published - 2015 |