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Title: Flow fields produced by acoustic resonances
Author: Marshall, S. B.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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This thesis investigates the velocity disturbance measurements around a single plate in a rectangular duct during a Flow Induced Acoustic Resonance (FIAR). A recirculating wind tunnel was designed and built specifically for Laser Doppler anemometry measurements of the flow. Detailed acoustic spectra were recorded through a velocity range which included the FIAR 'locked on' range. This revealed variations in the primary acoustic frequency through the range and showed the relevance of the Strouhal frequency bandwidth. The non-resonant and peak amplitude resonant cases were compared, which showed similarities between the mean velocity profiles. Following from this, a thorough examination of the velocity fields associated with the peak resonant case revealed the locations of the acoustic and velocity fluctuations. These locations were compared at four velocities within the FIAR range, covering the resonance lock on, peak, post peak and lock off. Convecting and non convecting velocity disturbances were found in these four cases. The area where the kinetic energy of the flow is periodically transferred to the acoustic pressure field was discovered. The positioning of a round bar downstream causes periodic changes in the resonance response envelope. Acoustic spectra were taken for five selected positions between the bar and plate. The spectra revealed the dominant features of the FIAR velocity range which were then investigated using the knowledge gained from the single plate work. The velocity disturbance waves were also found to occur in the case with the bar. This thesis has shown a new phenomenon which has not been previously addressed, namely the absorption by the acoustic pressure antinode in the Parker beta mode of the velocity disturbance wave leaving the leading edge.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available