Pore-Scale Simulation Of Experimentally Realizable, Oscillatory Flow In Porous Rock

We report new simulations of oscillating flow in porous rock. Our goal is to better understand the frequency dependence of pore-scale fluid motion, which should ultimately help us to interpret attenuation and electroseismic measurements. We use a lattice gas cellular automaton (Rothman and Zaleski, 1997) to perform the calculations in a pore space geometry measured from Fontainebleau sandstone by X-ray microtomography (Spanne et al., 1994; Auzerais et al., 1996). We chose this method because it is fast and efficient in the complex geometry of the porous rock. We show that the Biot critical frequency (Biot, 1956) is accessible to simulation, and we perform simulations at a range of frequencies around the critical frequency. In addition, we show that the dynamical properties of the lattice gas fluid can be mapped onto reasonable real fluids. As the frequency varies through the critical range, we observe qualitative and quantitative changes in the amplitude and phase of fluid velocity distributions. We also report preliminary calculations of the local viscous dissipation, which should provide a means to compare our simulations with existing theories of attenuation (e.g., Johnston et al., 1979; Dvorkin and Nur, 1993; Akbar et al., 1994).Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation ConsortiumSaudi Aramc

Cellular Metals: Fabrication, Properties and Applications

Cellular solids and porous metals have become some of the most promising lightweight multifunctional materials due to their superior combination of advanced properties mainly derived from their base material and cellular structure. They are used in a wide range of commercial, biomedical, industrial, and military applications. In contrast to other cellular materials, cellular metals are non-flammable, recyclable, extremely tough, and chemically stable and are excellent energy absorbers. The manuscripts of this Special Issue provide a representative insight into the recent developments in this field, covering topics related to manufacturing, characterization, properties, specific challenges in transportation, and the description of structural features. For example, a presented strategy for the strengthening of Al-alloy foams is the addition of alloying elements (e.g., magnesium) into the metal bulk matrix to promote the formation of intermetallics (e.g., precipitation hardening). The incorporation of micro-sized and nano-sized reinforcement elements (e.g., carbon nanotubes and graphene oxide) into the metal bulk matrix to enhance the performance of the ductile metal is presented. New bioinspired cellular materials, such as nanocomposite foams, lattice materials, and hybrid foams and structures are also discussed (e.g., filled hollow structures, metal-polymer hybrid cellular structures)

Massiv parallele Simulation von Mehrphasen- und Mehrkomponentenströmungen unter Anwendung des Lattice Boltzmann Verfahrens

This thesis reflects the work mainly performed within the research project FIMOTUM focusing on the determination of transport properties and mechanisms in unsaturated media. The efficient simulation of single- and multiphase flows at the pore scale in highly resolved natural porous media is one of the major topics in this work. For this purpose a simulation kernel which is based on the lattice Boltzmann method (LBM) has been developed and extensively validated. The LBM presented utilizes the Multiple Relaxation Time (MRT) model and fluid/wall boundary conditions of second order accuracy. The model has also been extended to solve multiphase, advection/diffusion and thermal flow problems. Due to the application of an optimized collision model and corresponding boundary conditions, the covered parameter space and the stability of the method could be greatly enhanced. Hence, it was possible to perform simulations in complex geometries at a large scale (2E11+ DoF) which have been obtained with an unprecedented accuracy. A second target of this thesis was the design and implementation of a simulation kernel to perform massively parallel computations with high efficiency. In order to obtain accurate simulation results at reasonable computational effort, a novel grid generation procedure has been developed. The robust and flexible method is based on the decoupling of input geometry and the actual computational grid. It is therefore excellently suited for the grid generation based on natural porous media data sets obtained by CT- or X-ray methods. Aspects concerning the increasing difficulties in pre- and post-processing of large data sets are discussed. Furthermore, special issues in high performance computing environments are highlighted and a tool chain to visualize scientific data in photo-realistic representation is described.Die vorliegende Dissertation gibt im Wesentlichen die Arbeiten wieder, die im Rahmen des FIMOTUM Projektes durchgeführt worden sind, welches sich vornehmlich auf die Untersuchung von Transporteigenschaften in ungesättigten porösen Medien fokussierte. Hierfür wurde ein Software-Prototyp auf Basis der Gitter Boltzmann Methode (LBM) entwickelt und ausführlich validiert. Die vorgestellte LB-Methode basiert auf dem Multiple-Relaxation-Time (MRT) Modell und verwendet Fluid/Wand Randbedingungen mit einer Genauigkeit 2. Ordnung. Das beschriebene Modell wurde zudem für die Simulation von Mehrphasen-, Advektion/Diffusions- und Thermalen Problemen erweitert. Durch die Optimierung des Kollisionsmodells und der entsprechenden Randbedingungen konnte der nutzbare Parameterraum deutlich vergrößert werden, so dass Simulationen in komplexen Geometrien mit mehr als 2.0E+11 Freiheitsgraden möglich wurden. Ein zweites Ziel dieser Arbeit war die Implementierung eines effizienten und hochparallelen Software-Prototypen zur Simulation von fluiddynamischen Problemen. Um möglichst genaue Ergebnisse bei mäßigem Ressourceneinsatz zu erzielen, wurde ein neuartiger Gittergenerierungsprozess entwickelt. Dieses robuste und flexible Verfahren basiert auf der Entkopplung von Eingangsgeometrie und dem eigentlichen Rechengitter. Daher eignet sich dieser Gittergenerator hervorragend für die Erzeugung eines numerischen Gitters aus digitalen Datensätzen natürlicher poröser Medien, wie bspw. Tomographie-Scans. Desweiteren werden, neben allgemeinen Problemen des Hochleistungsrechnens, die zunehmenden Schwierigkeiten bei der Verarbeitung der ständig steigenden Datenmengen im Pre- und Postprocessing diskutiert. Weiterhin wird, unterstützend zur Ergebnisanalyse, eine Prozesskette für die Erzeugung von fotorealistischen Visualisierungen aus Simulationsdaten beschrieben

Methodology for the production and delivery of generative music for the personal listener : systems for realtime generative music production

This thesis will describe a system for the production of generative music through specific methodology, and provide an approach for the delivery of this material. The system and body of work will be targeted specifically at the personal listening audience. As the largest current consumer of music in all genres of music, this represents the largest and most applicable market to develop such a system for. By considering how recorded media compares to concert performance, it is possible to ascertain which attributes of performance may be translated to a generative media. In addition, an outline of how fixed media has changed how people listen to music directly will be considered. By looking at these concepts an attempt is made to create a system which satisfies societies need for music which is not only commodified and easily approached, but also closes the qualitative gap between a static delivery medium and concert based output. This is approached within the context of contemporary classical music. Furthermore, by considering the development and fragmentation of the personal listening audience through technological developments, a methodology for the delivery of generative media to a range of devices will be investigated. A body of musical work will be created which attempts to realise these goals in a qualitative fashion. These works will span the development of the composition methodology, and the algorithmic methods covered. A conclusion based on the possibilities of each system with regard to its qualitative output will form the basis for evaluation. As this investigation is seated within the field of music, the musical output and composition methodology will be considered as the primary deciding factor of a system's feasibility. The contribution of this research to the field will be a methodology for the composition and production of algorithmic music in realtime, and a feasible method for the delivery of this music to a wide audience

Reversible Computation: Extending Horizons of Computing

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first

Fluid Flow and Heat Transfer in Cellular Solids

To determine the characteristics and properties of cellular solids for an application, and to allow a systematic practical use by means of correlations and modelling approaches, we perform experimental investigations and develop numerical methods. In view of coupled multi-physics simulations, we employ the phase-field method. Finally, the applicability is demonstrated exemplarily for open-cell metal foams, providing qualitative and quantitative comparison with experimental data

Reversible Computation: Extending Horizons of Computing

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first

Modeling stormwater transport through unsaturated green roof substrates

In recent decades there has been an increase in research regarding green roofs and similar technologies. This increased interest is driven by the requirements of urban development and its effects both on humans and the environment. Additionally, the predicted increase in weather severity in the future is raising concerns on the capabilities of urban environments and their stormwater management systems to cope with the increase. Green roofs can be used as a space-conscious solution for improving stormwater management in urban areas as well as contributing to, for example, building protection and pollution and noise reduction. In order to fully utilize them effectively for stormwater runoff reduction it is necessary to quantify their effect and optimize their performance in a given climate. This optimization can take the form of placement on structures or by design within the green roof construction itself. This work focuses on optimization of design by applying computational fluid dynamics and lattice Boltzmann theory to the soil growth substrate. Computational fluid dynamics is used for modeling the flow through the green roof growth substrate (soil layer) at the macrososcopic scale while a lattice Boltzmann model is applied to the mesoscopic (soil particle) scale. Using these methods, the efficacy at water retention and drainage of given soil particles and full-sized green roofs can be determined. This work covers the framework covering both scales however the methodology is applied only to the mesoscopic scale. The focus within the mesoscopic scale is primarily on the hydrophilicity of the particles in the soil and its impact on liquid imbibition. Also included is an exploration on the liquid-air interfacial area and liquid penetration depth to aid in the analysis of the results. The findings of the study suggest particle hydrophilicity plays an important role in the imbibition process, particularly under light to medium rainfall conditions. In addition a pore blocking phenomenon is identified which requires further analysis. Finally, plans for future work and the closure of the two-framework methodology proposed in this work is discussed

Lattice Boltzmann modeling for shallow water equations using high performance computing

The aim of this dissertation project is to extend the standard Lattice Boltzmann method (LBM) for shallow water flows in order to deal with three dimensional flow fields. The shallow water and mass transport equations have wide applications in ocean, coastal, and hydraulic engineering, which can benefit from the advantages of the LBM. The LBM has recently become an attractive numerical method to solve various fluid dynamics phenomena; however, it has not been extensively applied to modeling shallow water flow and mass transport. Only a few works can be found on improving the LBM for mass transport in shallow water flows and even fewer on extending it to model three dimensional shallow water flow fields. The application of the LBM to modeling the shallow water and mass transport equations has been limited because it is not clearly understood how the LBM solves the shallow water and mass transport equations. The project first focuses on studying the importance of choosing enhanced collision operators such as the multiple-relaxation-time (MRT) and two-relaxation-time (TRT) over the standard single-relaxation-time (SRT) in LBM. A (MRT) collision operator is chosen for the shallow water equations, while a (TRT) method is used for the advection-dispersion equation. Furthermore, two speed-of-sound techniques are introduced to account for heterogeneous and anisotropic dispersion coefficients. By selecting appropriate equilibrium distribution functions, the standard LBM is extended to solve three-dimensional wind-driven and density-driven circulation by introducing a multi-layer LB model. A MRT-LBM model is used to solve for each layer coupled by the vertical viscosity forcing term. To increase solution stability, an implicit step is suggested to obtain stratified flow velocities. Numerical examples are presented to verify the multi-layer LB model against analytical solutions. The model’s capability of calculating lateral and vertical distributions of the horizontal velocities is demonstrated for wind- and density- driven circulation over non-uniform bathymetry. The parallel performance of the LBM on central processing unit (CPU) based and graphics processing unit (GPU) based high performance computing (HPC) architectures is investigated showing attractive performance in relation to speedup and scalability