Master Theses & Projects (FEAS)

Permanent URI for this collectionhttps://hdl.handle.net/10155/687

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Browsing Master Theses & Projects (FEAS) by Subject "Acoustic damping"

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    Damping acoustic pressure pulsations in pipelines using Helmholtz resonators
    (2019-05-01) Sachedina, Karim; Mohany, Atef
    In industrial piping systems, centrifugal and reciprocating turbomachinery generate acoustic pressure pulsations, which propagate into the pipeline and interact with piping components, potentially causing vibrations, increased fretting wear, and even fatigue failure. In this thesis, an acoustic damping device known as the Helmholtz resonator (HR) is experimentally studied. The effects of HR cavity volume, pipeline diameter, HR location, the use of multiple HRs, and mean flow velocity are investigated to determine their effects on the acoustic attenuation achieved within a pipeline. Measurements are also performed to clarify the mechanism of attenuation and the effects of incident pressure amplitude on the transmission loss of an HR. The findings of this thesis may be used as practical guidelines for the use of HRs in industrial systems, where characterizing the acoustics is usually difficult and costly, and the available space for damping devices may be limited.
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    Parametric investigation of flow-sound interaction mechanism of circular cylinders in cross-flow
    (2016-12-01) Afifi, Omar; Mohany, Atef
    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 cylinders. Most of the research lately has therefore shifted focus to simpler geometries that resemble the same mechanisms of flow-sound interaction found in actual heat-exchangers. The research presented hereafter summarizes an extensive experimental parametric work performed on multiple simple configurations such as single, tandem and side-by-side cylinders in cross-flow. The main objective of the research is to identify the critical parameters that should be included in the damping criteria to reliably predict the occurrence of acoustic resonance in tube bundles. Special attention is given to the geometrical characteristics of the duct (i.e. cross-sectional area) and how they affect the acoustic resonance. To achieve this; more than one hundred experiments have been performed in three different wind-tunnels of different cross-sectional areas. The research is motivated by the fact that most of the criteria developed to date, fail to predict the destructive phenomena of acoustic resonance in 30-40% of the cases.