Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 27 for “"Acoustic resonance"”.
-
Passive methods for suppressing acoustic resonance excitation in shallow rectangular cavities.
The flow-excited acoustic resonance in shallow rectangular cavities can be a source of severe noise and/or excessive vibration. This phenomenon is excited when one of the acoustic modes in the accommodating enclosure is coupled with the flow instabilities resulting from the shear layer formation at …
-
Applications of Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) in pharmaceutical analysis
… tablet and liquid formulations called Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS). BARDS is an innovative technique that can economise production processes for drug formulations. BARDS is based on reproducible changes in a solvent's compressibility as a sample dissolves. It is a …
-
Flow characteristics and acoustic resonance excitation of finned cylinders in cross-flow
The flow characteristics and acoustic resonance excitation of bare and finned cylinders of different arrangements in cross-flow were experimentally investigated. In the design phase of finned tube heat exchangers, finned cylinders are treated as bare cylinders with a diameter equivalent to their …
-
Applications development of broadband acoustic resonance dissolution spectroscopy (BARDS) in the pharmaceutical, food and animal nutrition industries
Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) is a novel analytical tool for the characterisation of powders, blends, tablets and a myriad of formulations. It is based on a phenomenon which occurs during the dissolution of solid material in solution. When the sample is added the …
-
Parametric investigation of flow-sound interaction mechanism of circular cylinders in cross-flow
Flow-excited acoustic resonance in heat exchangers has been an ongoing issue for the past century. The main challenge in this issue, is in the actual prediction of the resonance occurrence. This is due to the complexity of the flow-sound interaction mechanism that takes place between the packed …
-
Effect of self-excited acoustic perturbations on flow characteristics around rectangular cylinders with varied geometrical aspects
… of such geometrical aspects to self-excited acoustic resonance in rectangular cylinders inside a high-speed wind tunnel. Experimental findings demonstrate a notable shift in both acoustic pressure and dynamic lift force during resonance excitation for rods characterized by an aspect ratio of …
-
Effect of diameter ratios on the flow-sound interaction of the straight circular finned cylinders
… could be susceptible to the flow-excited acoustic resonance that generates intense pressure fluctuations, which may lead to premature fatigue failure of the tubes. This thesis explores the unsteady flow development around circular finned tubes and its role in the excitation of acoustic …
-
Piezoceramic Actuated Transducers for Interior Acoustic Noise Control
… capacity of launch vehicles is to reduce the acoustic environment in the interior of the fairing. A major problem is that passive methods currently used for noise suppression do not exhibit significant energy dissipation at low frequencies. This motivates the use of active noise control. Using …
-
Linear 1-D analysis of oscillation instabilities in stationary plasma thrusters
… instabilities, it is believed that an ionization-acoustic resonance instability could be excited.
-
Passive damping mechanism of Herschel-Quincke tubes for pressure pulsations in piping systems
The acoustic pressure pulsations in industrial piping systems can induce fluctuating loads on inline equipment which may cause fatigue failure and in severe cases, initiate a phenomenon known as acoustic resonance. Passive damping devices such as the Herschel-Quincke (HQ) Tube can be implemented …
-
Flow-sound interaction mechanism of a single spirally finned cylinder in cross-flow
… the vortex shedding frequency and one of the acoustic cross-modes of the duct housing the finned tubes. This may reduce the service life of the heat exchangers, and adversely affect the health of individuals working in the proximity of such noise. Since the flow-acoustic phenomenon of finned …
-
Frequency Response Modeling of Additive Friction Stir Deposition Parts with Print Defects
… or geometry through processes such as laser acoustic resonance spectroscopy. This work focuses on leveraging vibration resonance to detect flaws in prints produced through additive friction stir deposition that arise through environmental contamination. More specifically, the use case …
-
BARDS analysis of real-time H2 and O2 gas evolution during the total water splitting of an aqueous electrolyte
… taking inspiration from existing Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) analytical technique. The BARDS technique observes the change in the resonance frequency of a solvent when a solute is added to the solution. This change in frequency occurs due to the formation of …
-
Magnetic and Elastic Interactions at Cracks and Interfaces in Ferromagnetic Materials
… through a coupling effect known as magneto-acoustic resonance. A model for the phenomena, in which magnetic waves excite elastic waves and vice versa, was formulated and used to explore the spin (magnon) and anti-plane elastic (phonon) interactions in piecewise homogeneous ferromagnetic …
-
Design and Validation of a Proportional Throttle Valve System for Liquid-Fuel Active Combustion Control
… capabilities, and relatively low cost. Using the acoustic resonance of the fuel line, the system is able to achieve 128% pressure modulation, relative to the mean pressure, and is capable of producing more than 75% flow modulation at 115 Hz. Additionally, at 760 Hz the system produces 40% pressure …
-
Flow induced acoustic resonances in heat exchangers.
This thesis describes an investigation into the acoustic phenomenon in in-line tubular heat exchangers subjected to cross flow. The flow through such a heat exchanger can result in the production of very high noise levels, which occur as a result of the excitation of an acoustic standing wave in …
-
System Identification and Optimization Methodologies for Active Structural Acoustic Control of Aircraft Cabin Noise
… via active control techniques. Active Structural Acoustic Control (ASAC) has shown much promise for reducing interior cabin noise in aircraft by applying control forces directly to the fuselage structure. Optimal positioning of force actuators for ASAC presents a challenging problem however, …
-
Feedback control of oscillations in combustion and cavity flows
… in a Rijke tube. Another type of fluid-acoustic resonance is then considered: the compressible flow past a shallow cavity. We start by finding a linear model of the cavity flow's dynamics, or its `transfer function', which we identify from direct numerical simulations. We compare this …
-
An Experimental Investigation of Self-Excited Combustion Dynamics in a Single Element Lean Direct Injection (LDI) Combustor
… NOx emissions, they promote a coupling between acoustics, hydrodynamics and combustion that can lead to combustion instabilities. These couplings can be quite complex, and their detailed understanding is a pre-requisite to any engine development program and for the development of predictive …
-
Three Dimensional Passive Integrated Electronic Ballast for Low Wattage HID Lamps
… ballast. However, a unique phenomenon called acoustic resonance could occur in HID lamps under high-frequency operation. A low-frequency square wave current driving scheme has proved to be the only effective method to avoid acoustic resonance in HID lamps. A typical electronic HID ballast …
Page 1 of 2