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Numerical Modeling of Propagation of Sound Waves in an Inhomogeneous and Moving Medium of the Atmospheric Troposphere Layer

Hamidzadeh, Mohammad Hossein | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45719 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Taeibi Rahni, Mohammad; Massah, Hamid Reza
  7. Abstract:
  8. Troposphere layer includes complex flows which their effects in acoustic sensors are indicated as acoustic wave noise.It is essential to analyze these complex flows to recognize how to reduce the noise. In this thesis we have perused and modeled the sound wave propagation in troposphere layer.Given data are some thermal and velocity profiles of atmospheric flowsthe assumptions are: 1- gravity waves are negligible, 2- air density depends only on altitude, 3- sound waves parabolic equation assumptions are applied. Our goal Is to find the sound pressure level originated from a sound source in troposphere layer.This thesis emphasizes on analysis, recognition and modeling of the problem. Main Innovations of this thesis are: 1- modeling of effects of inhomogeneous and moving atmosphere on sound propagation in troposphere layer,2- Precise calculation of received sound waves in sensors in order to noise reduction. The procedure is: 1- review of troposphere layer structure, 2- review of sound propagation in atmosphere and explanation of sound distributions mechanism,3- review of inhomogeneous atmosphere and atmospheric flows in Troposphere layer,4- study of interaction of wind and inhomogeneous atmosphere with sound waves 5- solving the parabolic equation of sound wave propagation in an inhomogeneous and moving medium in troposphere layer by Crank-Nicholson finite difference method.Upper boundary condition is arranged to minimize the reflection into calculation region.Because of analyzing in long range, low frequencies are studied.Results show that sound velocity profile is affected by wind velocity and temperature.Although surface roughness, earth impedance, source elevation and frequency have an effect on sound propagation
  9. Keywords:
  10. Atomosphere ; Numerical Modeling ; Sound Propagation ; Inhomogeneous Medium ; Troposphere Layer

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