Influência do módulo de compressibilidade na propagação da onda acústica em meios estratificados
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Data
2023-09-29
Autores
Araujo, Luana Maria Kiefer de
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Universidade Federal do Espírito Santo
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This dissertation focuses on investigating the influence of compressibility modulus on acoustic propagation in stratified media. Fluid mechanics approaches are employed to derive the equation governing the propagation of acoustic waves in a non-homogeneous medium. A second-order partial differential equation (PDE), considering both space and time, is formulated to describe the propagation of the pressure wave, also known as the P-wave, and incorporates a Mexican hat-shaped source term that models the disturbance generated in the medium. To numerically solve the P-wave PDE, the finite difference method in the time domain is implemented, using a second-order explicit scheme in both time and space. To ensure numerical stability, a stability condition is developed that adjusts the time step according to the spatial discretization of the numerical mesh. Within the numerical solution context, a second-order Absorbing Boundary Condition (ABC) is applied. The numerical model is implemented in FORTRAN and integrated with the OCTAVE and PYTHON environments to facilitate result visualization. Densities and wave velocities for a section along the coast of Espírito Santo are calculated based on temperature and salinity data obtained from the Hybrid Coordinate Ocean Model (HYCOM). Subsequently, the compressibility modulus is computed, and simulations of P-wave propagation in real oceanic scenarios are conducted to gain a deeper understanding of its role in the propagation of acoustic waves in non-homogeneous media. The simulations underscore the critical importance of wave velocity due to its direct influence on wave travel times, especially relevant in applications such as underwater seismology, where the precise location of seismic sources depends on these times. In the research context, the compressibility modulus is acknowledged as significant, though its fluctuation in seawater is considerably smaller compared to variations in sound velocity. This discrepancy assigns a prominent role to sound velocity in the analysis and interpretation of seismic and acoustic data
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