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| 2. |
- Jänicke, Ralf, 1980
(författare)
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Computational homogenization and reduced order modeling of dif- fusion processes in fluid-saturated porous media
- 2016
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Fluid-saturated porous media are well-known for their manifold attenuation mechanismscaused by wave-induced fluid flow between microscopic or mesoscopic heterogeneities. Ifelastic waves propagate through such a medium, the pore space is heterogeneously com-pacted resulting in local pressure gradients. These pressure gradients are equilibrated bya redistribution of the viscous pore fluid (water, gas, oil, etc.), which causes pore pressurediffusion. Hereby, part of the wave energy is lost, and the wave is attenuated. In thiscontribution, we concentrate on the upscaling behavior of fluid-saturated rocks featuringdouble porosity, patchy saturation or networks of fluid conduits. Based on Biot’s quasi-static equations of consolidation and an appropriate hybrid-dimensional description ofthe fracture networks, we establish a computational homogenization framework. To thisend, we assume the pressure diffusion to occur within mesoscopic volume elements muchsmaller than the macroscopic wave length. Hence, diffusion takes place on a length scalemuch smaller than the observer scale and is considered, from the macroscopic viewpoint,as a local process. The heterogeneous poroelastic medium, therefore, is substituted bya homogeneous macroscopic Cauchy medium with apparent viscoelastic properties. Thematerial properties of the substitute model are derived making use of a novel order reduc-tion technique allowing for a numerically efficient treatment of the scale-transition. Themacroscopic internal variables representing the overall viscoelasticity are interpreted asparameters controlling the activity of mesoscopic pressure modes identified by the ProperOrthogonal Decomposition (POD) technique. We show that the resulting decoupled sys-tem of evolution equations is equivalent to that of a generalized Maxwell-Zener model.In the second part of this contribution we weaken the locality constraint and allow formacroscopically observable seepage of the pore fluid. Hence, the character of the ho-mogenization problem changes and the macroscopic substitute medium is considered as aporoviscoelastic material. We derive a consistent computational homogenization schemeand enrich the proposed order reduction concept by the required additional features. Thecontribution is completed by numerous numerical investigations including validation testsand extensive discussions of our findings.
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| 3. |
- Parasnis, Dattatray
(författare)
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Mining geophysics
- 1973. - 2 rev.
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Bok (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Parasnis, Dattatray
(författare)
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Principles of applied geophysics
- 1986. - 4
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Anyone who compares the present thoroughly revised and enlarged edition of this book with the three previous ones, the first of which was published in 1962, may well ask whether the principles of applied geophysics have become more numerous during the last 25 years or so. Such is not the case and the much larger size of the present edition is due to the principles' having been explained in greater detail than heretofore. There are major and minor alterations, additions and emendations, too numerous to be listed here, throughout the book but I would like to draw attention specifically to some of them. The chapter on seismic methods is now far more extensive than before and so are also the chapters on electric and electromagnetic methods. There is also a separate chapter on well logging in oil fields giving the essential ideas. Considering the virtual plethora of available books on seismic methods and on well logging I have not thought it necessary to extend these chapters further. This has enabled me to keep the book to a reasonable length and at the same time retain its fairly comprehensive character. Other features of the present edition are solved examples in the text and the problems at the end of all principal chapters. Answers and hints to the latter are given at the end of the book.
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| 6. |
- Sjöberg, Lars E., et al.
(författare)
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Gravity Inversion and Integration : Theory and Applications in Geodesy and Geophysics
- 2017
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This book contains theory and applications of gravity both for physical geodesy and geophysics. It identifies classical and modern topics for studying the Earth. Worked-out examples illustrate basic but important concepts of the Earth’s gravity field. In addition, coverage details the Geodetic Reference System 1980, a versatile tool in most applications of gravity data.The authors first introduce the necessary mathematics. They then review classic physical geodesy, including its integral formulas, height systems and their determinations. The next chapter presents modern physical geodesy starting with the original concepts of M.S. Molodensky. A major part of this chapter is a variety of modifying Stokes’ formula for geoid computation by combining terrestrial gravity data and an Earth Gravitational Model.Coverage continues with a discussion that compares today’s methods for modifying Stokes’ formulas for geoid and quasigeoid determination, a description of several modern tools in physical geodesy, and a review of methods for gravity inversion as well as analyses for temporal changes of the gravity field.This book aims to broaden the view of scientists and students in geodesy and geophysics. With a focus on theory, it provides basic and some in-depth knowledge about the field from a geodesist’s perspective.
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