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Seaquake waves - standing wave dynamics with Faraday excitation and radiative loss /Dolven, Eric T. January 2002 (has links)
Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 130-134).
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Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluidErickson, Andrew Jay 23 April 2013 (has links)
In this paper we develop a computational procedure to investigate linear fracture of two-dimensional problems in isotropic linearly elastic media. A symmetric Galerkin boundary element method (SGBEM), based on a weakly singular, weak-form traction integral equation, is adopted to model these fractures. In particular we consider multiple interacting cracks in an unbounded domain subject to internal pressure and remote stress. The growth of the cracks is driven by either linearly dependent injection pressures or volumes in each crack. A variety of crack geometries are investigated. / text
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Leading edge vortex modeling and its effect on propulsor performanceTian, Ye, active 21st century 09 February 2015 (has links)
A novel numerical method solves the VIScous Vorticity Equation (VISVE) in 3D in order to model the Leading Edge Vortex (LEV) of propellers is proposed and implemented in this dissertation. The spatial concentration of the vorticity is exploited in the method, which is designed to be spatially compact and numerically efficient, in the meantime, capable of modeling complicated vorticity/solid boundary interaction in 2D and 3D. The numerical model can work as a viscous correction on top of the traditional Boundary Element Method (BEM) results. The proposed method is first applied in the case of a 2D hydrofoil at high angle of attack. The results are correlated with those from Navier-Stokes (N-S) simulation. The method is then used to model the LEV and tip vortex of a 3D swept wing. The results of the 3D simulation show great similarity to those from N-S. In the end, the method is applied in the case of propellers at low advance ratios. All the essential flow characteristics (LEV and tip vortex) are predicted. The objective of this dissertation is not developing a mathematically equivalent numerical method to the full-blown Reynolds-Averaged Navier-Stokes (RANS) solver, but inventing an accurate and computationally efficient tool to model the effects of the LEV on the propeller performance for engineering's purpose. / text
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Boundary/finite element meshing from volumetric data with applicationsZhang, Yongjie 28 August 2008 (has links)
Not available / text
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Thermo-Poroelastic Fracture Propagation Modeling with Displacement Discontinuity Boundary Element MethodChun, Kwang Hee 16 December 2013 (has links)
The effect of coupled thermo-poroelastic behavior on hydraulic fracture propagation is of much interest in geothermal- and petroleum-related geomechanics problems such as wellbore stability and hydraulic fracturing as pore pressure and temperature variations can significantly induce rock deformation, fracture initiation, and propagation. In this dissertation, a two-dimensional (2D) boundary element method (BEM) was developed to simulate the fully coupled thermo-poroelastic fracture propagation process. The influence of pore pressure and temperature changes on the fracture propagation length and path, as well as on stress and pore pressure distribution near wellbores and fractures, was considered in isotropic and homogeneous rock formations.
The BEM used in this work consists of the displacement discontinuity (DD) method and the fictitious stress (FS) method. Also, a combined FS-DD numerical model was implemented for the hydraulically or thermally-induced fractures in the vicinity of a wellbore.
The linear elastic fracture mechanics (LEFM) theory was adopted to numerically model within the framework of poroelasticity and thermo-poroelasticity theory. For high accuracy of crack tip modeling, a special displacement discontinuity tip element was developed and extended to capture the pore pressure and temperature influence at the tip. For poroelastic fracture propagation, a steadily propagating crack driven by fluid pressure was modeled to find the effect of pore pressure on crack path under the two limiting poroelastic conditions (undrained and drained). The results indicate that the pore pressure diffusion has no influence on the crack growth under the undrained condition because the crack propagation velocity is too fast for the diffusion effect to take place. On the other hand, its influence on the crack path under the drained condition with its low propagation velocity has significance because it induces a change in principal stress direction, resulting in an alteration of fracture orientation.
For the thermal fracturing, when the rock around a wellbore and a main fracture is cooled by injecting cold water in a hot reservoir, the rapid decrease in temperature gives rise to thermal stress, which causes a crack to initiate and propagate into the rock matrix. The single and multiple fracture propagation caused by transient cooling in both thermoelastic and poro-thermoelastic rock were numerically modeled. The results of this study indicate that the thermal stresses induced by cooling may exceed the in-situ stress in the reservoir, creating secondary fractures perpendicular to main fracture. Furthermore, the faster cooling rate produces longer crack extension of the secondary thermal fractures. This implies that the faster cooling induces a higher tensile stress zone around the fracture, which tends to produce larger driving forces to make the secondary fractures penetrate deeper into the geothermal reservoir.
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On the evaluation of hyper-singular integrals arising in the boundary element method for elasticity and acoustic problemsChien, Chyou-Chi 08 1900 (has links)
No description available.
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Inverse Problems in Soft Tissue Elastography using Boundary Element MethodsBerger, Hans-Uwe January 2009 (has links)
Elastography is an emerging functional imaging technique of current
clinical research interest due to a direct relation between
mechanical material parameters, especially the tissue stiffness, and
tissue pathologies such as cancer. Digital Image Elasto-Tomography
(DIET) is a new method that aims to develop elastographic techniques
and create a simplified, improved breast cancer screening process.
The elastic material information of breast tissue is reconstructed
in the DIET concept from mechanically excited steady-state harmonic
motion observed on the surface of the breast. While this inversion
process has been traditionally approached using finite element
methods, this surface-orientated problem is naturally suited to the
use of Boundary Element Methods (BEMs) requiring the discretization
only on the surface of the domain and on the interface of a
potential inclusion. As only approximate information is available
about breast tissue material parameters, this thesis presents the
development of BEM based inverse problem algorithms suitable for the
reconstruction of all material parameters in a proportionally damped
isotropic linear elastic solid, where only the material density is
known. The highly nonlinear identification process of a potential
inclusion is treated through the combination of a systematic
Grid-Search with gradient descent techniques. This algorithm is
extended to a three-step algorithm that performs a background
material parameter estimation before the subsequent identification
of an inclusion and thus provides a confident indication for the
differentiation between cancerous and healthy breast tissue. The
development of these algorithms is illustrated by several simulation
studies highlighting important reconstruction behaviors relevant to
the elastographic inverse problem. A first experimental test on a
silicon based breast phantom is presented.
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DESIGN OF PARTIAL ENCLOSURES FOR ACOUSTICAL APPLICATIONSCarter, Amy Elizabeth 01 January 2006 (has links)
Enclosures are a very common way to reduce noise emissions from machinery. However, enclosures display complex acoustic behavior that is difficult to predict. The research presented in this thesis uses the boundary element method in order to better understand the acoustic behavior of a partial enclosure. Insertion loss was used as the performance measure and the effect of several design factors on the overall insertion loss was documented. Results indicate that the most important factors affecting enclosure performance are the opening size, amount of absorption, and the source-to-opening distance.
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Some problems in anisotropic elasticity / Tristom Peter Cooke.Cooke, Tristrom Peter January 1998 (has links)
Bibliography: leaves 91-95. / x, 155 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis contains methods of solution for a number of different problems within the area of the elasticity of anisotropic materials. The first problem concerns the calculation of stresses and strains within a concentric arrangement of cylindrical shells, where each shell has a differing set of anisotropic properties. This has immediate application to the design of yacht masts, and the particular example of the "Moth" yacht mast is considered. The second problem considered is the uncoupled thermo-elastic problem, where a boundary element method is derived for solving the class of boundary value problems governing plane thermo-elastic deformations of isotropic and anisotropic materials. The final class of problems deals with mixed boundary value problems in which the stresses become singular at some points, for instance in elastic problems containing cracks. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 1998
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Enhancing the scaled boundary finite element method /Vu, Thu Hang. January 2006 (has links)
Thesis (Ph.D.)--University of Western Australia, 2006.
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