Thermoacoustic wave propagation in a two-dimensional rectangular cavity is studied numerically. The thermoacoustic waves are generated by raising the temperature locally at the walls. The waves, which decay at large time due to thermal and viscous diffusion, propagate and reflect from the walls creating complicated two-dimensional patterns. The accuracy of numerical simulation is ensured by usi...

Thermophones are highly promising for applications such as high-power SONAR arrays, flexible loudspeakers, and noise cancellation devices. So far, freestanding carbon nanotube aerogel sheets provide the most attractive performance as a thermoacoustic heat source. However, the limited accessibility of large-size freestanding carbon nanotube aerogel sheets and other even more exotic materials rec...

Microwave-induced thermoacoustic tomography (MI-TAT) is an imaging technique that exploits dielectric contrast at microwave frequencies while creating images with ultrasound resolution. We propose the use of microbubbles as a dielectric contrast agent for enhancing the sensitivity of MI-TAT for breast cancer detection. As an initial investigation of this concept, we experimentally studied the e...

Title of Document: THERMOACOUSTIC-PIEZOELECTRIC SYSTEMS WITH DYNAMIC MAGNIFIERS Mostafa Nouh, Doctor of Philosophy, 2013 Directed By: Professor Amr Baz Department of Mechanical Engineering Thermoacoustic energy conversion is an emergent technology with considerable potential for research, development, and innovation. In thermoacoustic resonators, self-excited acoustic oscillations are induced i...

Experiments with an annular thermoacoustic engine employing quasiadiabatic interaction between traveling acoustic waves and an inhomogeneously heated porous material indicate the presence of a closed-loop mass flux. A qualitative modeling of the enthalpy flux in the thermoacoustic core provides an opportunity to estimate the thermal convection associated with this mass flux, by using temperatur...

Motivation Fuel lean combustion is often employed to reduce pollutant emissions (CO, NOx,...) and increase gas turbine lifetime via reduced temperature. However, lean combustion is susceptible to thermoacoustic instabilities and lean blowout (LBO). Thermoacoustic instabilities are due to the coupling of heat release to acoustic oscillations, and lead to reduced combustion efficiency and increas...

In a time of heightened environmental concerns and increased importance on efficiency, thermoacoustic standing waves and oscillations provide a possible solution to many contemporary problems. Elementary standing wave theory is discussed, as well as the connection between thermodynamics and acoustical oscillations. Additionally, the benefits of Sondhauss oscillations and devices for their produ...

Our study on pulsed-microwave-induced thermoacoustic tomography in biological tissues is presented. A filtered backprojection algorithm based on rigorous theory is used to reconstruct the cross-sectional image from a thermoacoustic measurement in a circular configuration that encloses the sample under study. Specific details describing the measurement of thermoacoustic waves and the implementat...

Recently, active control has been pursued vigorously for combating thermoacoustic instabilities in the combustion process. While many of the reported experiments, with controllers that include filter components determined by trial and error, have demonstrated that the dominant thermoacoustic instability can be suppressed, often the response contains secondary peaks at other frequencies which we...