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Wind and Turbulence Effects on Long-range Sound Propagation in Troposphere Layer

Karimpour, Zahra | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48742 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Taeibi-rahni, Mohammad; Massah, Hamid Reza
  7. Abstract:
  8. Considering atmospheric wave propagation as a complex phenomenon, it can be represented as a function of variety of parameters such as: properties of atmosphere, boundary conditions, surface characteristics, source related parameters and etc. the aim of this work is to study the propagation of sound mechanisms in troposphere layer and numerical simulation of sound field in order to investigate the wind effect and turbulence in wave propagation. In this manner, the Green’s function parabolic equation (GFPE) is hired to solve the governing equation for sound propagation in a moving inhomogeneous atmosphere. To achieve this, a code is generated using MATLAB software to predict the long range sound field of a given source over flat ground in a moving inhomogeneous turbulent atmosphere. Since study the wind effect and turbulence in inhomogeneous atmosphere requires considering multiple factors, then taking simultaneously all these factors into account is one of the prominent aspects of this study. Also, inadequate research in atmospheric acoustic field of study made this dissertation a pioneer in this field. In addition to that, growing importance of the sound propagation studies motivated this research. The obtained results are in complete agreement with benchmark cases. The results show for downwind and /or positive gradient of temperature, sound pressure levels are not affected by the atmospheric turbulence and due to numerous reflections, the long-range propagation will be enhanced. On the other hand, in case of negative temperature gradient and/or upwind propagation, an acoustics shadow zone will be appeared near the ground surface. In such situation, due to atmospheric turbulence, the values of sound pressure levels will be enhanced in this region. Furthermore, maximum attenuation will be occurred in the presence of negative temperature gradient and/or upwind propagation and its intensity will be depended on the wind and temperature profiles. The results of this research are beneficial to different areas such as city planning, aviation, aerology, aerospace and etc
  9. Keywords:
  10. Sound Propagation ; Winds ; Turbulence ; Numerical Simulation ; Parabolic Equations ; Inhomogeneous Atmosphere ; Green's Function Parabolic Equation

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