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Measurement and Numerical Analysis of Submerged Propellers Noise in Far Field

Bagheri, Mohammad Reza | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48210 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Seif, Mohammad Saeed; Mehdigholi, Hamid
  7. Abstract:
  8. This thesis is concerned with measurement and analysis of noise for an underwater propeller by means of numerical and experimental methods. A major cause of noise in buoyant bodies is the propeller. Detection and measurement of such noise is a part of various engineering and maritime applications. Thus detecting the sources of sound and ways of its propagation under water is the first step in many engineering and maritime applications of underwater acoustics which leads to noise reduction and control. Due to its wide subject, this thesis presents a phenomenology of propeller noise and discusses numerical and experimental methods. In the section that deals with numerical methods, the hydrodynamics of various propeller models under different operational conditions is discussed. Then the conditions of cavitation initiation and development and the effect of water current velocity, propeller's rotational velocity and pressure drop as well as their impact on propeller noise is completely studied. Finally, in the numerical method section, sound pressure levels with and without cavitation are worked out and compared. We have outlined the phenomenology and impact of each factor on propeller operation and noise that are not completely discussed in previous research in particular for cavitation cases. The numerical study in this thesis is helpful for carrying out experiments. It is noteworthy that no previous research has been published on the propeller models that are considered in this thesis. In the second section of this thesis, equipping the cavitation tunnel and preparing the test environment in order to measure the sound pressure level is presented which is important for noise detection in sonar technology and underwater noise measurement. A major contribution of this thesis is a phenomenology and thorough study of all parameters in non-cavitation cases as well as the conditions for initiation and development of cavitation. Moreover, a complementary part of the thesis is dedicated to presenting a new method for propeller noise reduction that considers using the Inter sleek 700 silicon covering to delay cavitation as the main source of noise. In another section of this thesis the sound source for non-cavitation case is worked out from the acoustic pressure domain by means of an analytical program, a method that has not been employed in previous research
  9. Keywords:
  10. Inverse Method ; Cavitation Tunnel ; Propeller Noise ; Propeller Hydrodynamic ; Cavitation Inception ; Ffowcs Williams and Hawkings (FWH)Equation ; Cavitation Development

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