Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 54 for “"Acoustic scattering"”.
-
Acoustic Scattering by Gratings
This thesis considers the sound scattering by thin perforated plates, to further understand and develop analytic models for porous noise reduction metamaterials. The semi-analytic Fokas method is extended to periodic geometries, and the resulting integral equation, recognised as a generalised …
-
Acoustic Scattering in Sheared Flow
… well-understood and unavoidable source of noise, scattering vortical, hydrodynamic disturbances within the boundary-layer into far-field, acoustic, noise. Inspired by nature, for example the silent flight of owls, modification of the flow within the boundary-layer near the trailing-edge, either …
-
Acoustic scattering by discontinuities in waveguides
The scattering of acoustic waves by boundary discontinuities in waveguides is analyzed using the Method of Matched Asymptotic Expansions (MAE). Existing theories are accurate only for very low frequencies. In contrast, the theory developed in this thesis is valid over the entire range of …
-
Three-dimensional acoustic scattering from arctic ice proturberances.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995.
-
Qualitative methods far acoustic scattering inverse problems in wavequides
En esta tesis se investiga cómo el método de la derivada topológica puede aplicarse al estudio de la reconstrucción de la forma de un obstáculo dentro de una guía de ondas acústica tubular en el dominio de frecuencias. En particular, se deduce una expresión de la derivada topológica en términos de …
-
Acoustic scattering analysis for remote sensing of manganese nodules
The theory of the scattering of plane waves in a fluid medium by an isotropic elastic sphere representing a manganese nodule is developed. Scattering cross sections were computed using the theory and the results are presented graphically. The scattering cross section and the reflectivity factor …
-
Efficient Spectral-Element Methods For Acoustic Scattering And Related Problems
… development of high-order numerical methods for acoustic and electromagnetic scattering problems, and nonlinear fluid-structure interaction problems.</p> <p>For the scattering problems, two cases are considered: 1) the scattering from a doubly layered periodic structure; and 2) the scattering …
-
Amplitude fluctuation effects in shallow water acoustic scattering by internal waves
… the amplitude fluctuation effects in acoustic scattering due to shallow water internal waves. Theoretically, it uses the adiabatic approximation and perturbation methods to statistically evaluate acoustic transmission fluctuations caused by internal waves in the ocean; it also …
-
Acoustic scattering in waveguides with smoothly-varying or discontinuous elastic boundaries
A method for solving boundary-value problems where a boundary parameter varies continuously in space is applied to some canonical waveguide problems. The method, previously employed by Roseau and Evans, generates a functional difference equation, the solution to which enables fluid velocity …
-
Investigation of defects on acoustic scattering in cloak by molding process
… was developed in order to replicate the acoustic cloak. The metal was cast into a stretchable PDMS mold, which was cast from micromachined aluminum cloak. For the PDMS mold, the mold release agent, trichlorosilane ([tridecafluoro-1,1,2,2-tetrahydrooctyl] trichlorosilane), was enhanced to …
-
Amplitude fluctuation effects in shallow water acoustic scattering by internal waves
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995.
-
Normal mode acoustic scattering considering elastic layers over a half space
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1997.
-
Finite element-boundary elements modelling of acoustic scattering from viscoelastic anechoic structures
… to provide accurate numerical solutions to the acoustic scattering problem. A tile made of three layers, a reflecting aluminium layer, an absorbing butyl rubber layer and a matching layer made of a regular grid of polyurethane cones is finally analysed in several scattering and geometrical …
-
On the Factorisation of Matrix Wiener–Hopf Kernels Arising From Acoustic Scattering Problems
… consider three separate and distinct problems of acoustic scattering with rectangular geometries, which have a common underlying mathematical structure. The geometries are: the infinite wedge, the waveguide with a barrier, and the semi-infinite plate of finite thickness. It turns out that these …
-
Mid-frequency acoustic scattering from finite internally-loaded cylindrical shells near axial incidence
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995.
-
Acoustic scattering by axisymmetric finite-length bodies with application to fish : measurement and modeling
This thesis investigates the complexities of acoustic scattering by finite bodies in general and by fish in particular through the development of an advanced acoustic scattering model and detailed laboratory acoustic measurements. A general acoustic scattering model is developed that is accurate …
-
Acoustic scattering of spherical directional waves by smooth and statistically rough solid elastic cylinders
… incident plane wave. This thesis analyzes acoustic scattering by solid elastic cylinders insonified by realistic sonars both theoretically and experimentally. A theoretical model to predict scattering by arbitrary-length cylinders is derived based on the apparent volume flow accounting for …
-
Implementing and testing a panel-based method for modeling acoustic scattering from CFD input
… by its dependence on the geometry of the scattering surface---the aircraft carrier deck, aircraft control surfaces and other nearby structures.</p> <p>In this work, a time-domain boundary element method, or TD-BEM, (sometimes referred to in terms of source panels) is proposed and developed …
-
Acoustic scattering by axisymmertic finite-length bodies with application to fish : measurement and modeling
This thesis investigates the complexities of acoustic scattering by finite bodies in general and by fish in particular through the development of an advanced acoustic scattering model and detailed laboratory acoustic measurements. A general acoustic scattering model is developed that is accurate …
-
Acoustic scattering of spherical directional waves by smooth and statistically rough solid elastic cylinders
… incident plane wave. This thesis analyzes acoustic scattering by solid elastic cylinders insonified by realistic sonars both theoretically and experimentally. A theoretical model to predict scattering by arbitrary-length cylinders is derived based on the apparent volume flow accounting for …
Page 1 of 3