A generic formulation for modeling the sub-grid combustion in compressible, high Reynolds number, two-phase, reacting flows has been developed and validated. A sub-grid mixing/combustion model called Linear Eddy Mixing (LEM) model has been extended to compressible flows and used inside the framework of Large Eddy Simulation (LES) in this LES-LEM approach. The LES-LEM approach is based on the proposition that the basic mechanistic distinction between the convective and the molecular effects should be preserved for accurate prediction of the complex flow-fields such as those encountered in many combustion systems. In LES-LEM, all the physical processes such as molecular diffusion, small and large scale turbulent convection and chemical reaction are modeled separately but concurrently at their respective time scales. This multi-scale phenomena is solved using a two-scale numerical approach, wherein molecular diffusion, small scale turbulent convection and chemical reaction are grouped as small scale processes and the convection at the (LES grid) resolved scales are deemed as the large scale processes. Small-scale processes are solved using a hybrid finite-difference Monte-carlo type approach in a one-dimensional domain. Large-scale advection on the three-dimensional LES grid is modeled in a Lagrangian manner that conserves mass. Liquid droplets (represented by computational parcels) are tracked using the Lagrangian approach wherein the Newton's equation of motion for the discrete particles are integrated explicitly in the Eulerian gas field. Drag effects due to the droplets on the gas phase and the heat transfer between the gas and the liquid phase are explicitly included. Thus, full coupling is achieved between the two phases in the simulation. Validation of the compressible LES-LEM approach is conducted by simulating the flow-field in an operational General Electric Power Systems' combustor (LM6000). The results predicted using the proposed approach compares well with the experiments and a conventional (G-equation) thin-flame model. Particle tracking algorithms used in the present study are validated by simulating droplet laden temporal mixing layers. Comparison of the energy growth in the fundamental and sub-harmonic mode in the presence and absence of the droplets shows excellent agreement with spectral DNS. Finally, to test the ability of the present two-phase LES-LEM in simulating partially premixed combustion, a LES of freely propagating partially premixed flame in a droplet-laden isotropic turbulent field is conducted. LES-LEM along with the spray models correctly captures the flame structure in the partially premixed flames. It was found that most of the fuel droplets completely vaporize before reaching the flame, and hence provides a continuous supply of reactants, which results in an intense reaction zone similar to a premixed flame. Some of the droplets that did not evaporate completely, traverse through the flame and vaporize suddenly in the post flame zone. Due to the strong spatial variation of equivalence ratio a broad flame similar to a premixed flame is realized. Triple flame structure are also observed in the flow-field due to the equivalence ratio fluctuations.

In the study, an innovative method is developed in 2-D wave flume tests to explore how much sand is set in motion by waves, and how wave-moved sediment is related to wave properties. Wave conditions on an initial sea bed slopes with grain size of about 0.1mm are varying during the experiments. Three initial bottom slopes of 1/30, 1/45, and 1/60 are analyzed in the study. The total number of waves acting is about 39,600 for each wave condition. The accumulated time of generated waves during the study is more than 1,280 hours; this is equivalent to about 2.45 million waves. The dark sands, along the observing window of the wave tank, of an initial sea bed are replaced by a slice column of white sands. The mixing caused by the waves moved dark and white sands together which generates a layer of grey sands that marks the interface of moved and unmoved white sands on the window. In some cases, three additional white sand columns are merged into the dark sand body perpendicular to the window to verify the uniformity of the moved layer in the wave crest direction. The quantity of the moved sediment is then computed and the wave-moved sediment by each wave is evaluated. Results show that the wave-moved sediment by each wave is linearly correlated to the wave breaking induced turbulent eddy viscosity, based on Prandtls mixing length model. The corresponding proportional coefficient reaches an asymptotic value as the number of acting waves is more than about 10,000. A Similar trend, but more diverse, is found when the wave-moved sediment is related to a movable parameter defined from the Shields number in which the Komars relation of bottom friction and slope is applied. However, the results indicate that the wave-moved sediment does not linearly correlate with the breaking wave power as proposed by most previous studies.

The sources and sinks of energy for transient waves in the Martian atmosphere are investigated, applying diagnostic techniques developed for the analysis of terrestrial baroclinic waves to output from a Mars General Circulation Model. These diagnostic techniques include the vertically averaged eddy kinetic energy and regression analysis. The results suggest that the primary source of the kinetic energy of the waves is baroclinic energy conversion in localized regions. It is also shown that there exist preferred regions of baroclinic energy conversion. In addition, it is shown that downstream baroclinic development plays an important role in the evolution of the waves and in the baroclinic energy conversion process. This is the first time that evidence for downstream baroclinic development has been found for an atmosphere other than the terrestrial one.

While evaluating the depth of corrosive defect through Remote Field Eddy Current (RFEC) Testing technology, the researcher tried to investigate the signals of supporting plate which may produce variations by the thickness of supporting plate, diameter of tube hole in supporting plate, the value of crevice between tube and tube hole and tube wall thickness. Errors of evaluation of defect depth may consequently be identified or measured by the variations of the support plate signal. This study explores the effects of above four factors by experiments and an analysis of variance in statistics. By the analysis of experimental results, the researcher found the four influential factors would cause angle deviation of supporting plate signals. Except the factor of tube wall thickness, the deviation is not so substantial that the difference of evaluation in depth was consequently fallen into an acceptable range of engineering practices. When utilizing the remote field eddy current testing technique to test inservice tubes, the researcher found the thickness of inservice tube is normally different from the specified thickness of a standard tube. This variation consequently resulting in an evaluation curve produced by a standard tube may not lead to proper assessment of defects in inservice tube. To deal with the problem many researchers used a frequency compensation method to compensate for the evaluation error contributed by the variation of tube thickness on the basis of the standard ASTM E2096-00(2000). But the use of the frequency compensation method did not measure the inservice tube thickness and thus produced a drawback of consuming much time for the adjustment steps of compensation. Therefore, a mathematical compensation method was introduced in this study for the compensation of thickness variation derived from skin depth theory. This method in the present experiment is proven to be both feasible and reasonable through the derivation of the methodology. Generally, this study aims to apply the mathematical compensation method to overcome the drawback of frequency compensation method and to solve the problem of the difficulty in measuring inservice tube wall thickness in heat exchanger bundles.

Study of turbulent flow over a rough bed is highly important due to its numerous applications in the areas of sediment transport and pollutant discharge in streams, rivers and channels. Over the past few decades, many experimental studies have been conducted in this respect to understand the underlying phenomenon. However, there is a scarcity in the number of computational studies conducted on this topic. Therefore, a Large Eddy Simulation (LES) of turbulent flow over a rough channel bed was conducted to contribute further understanding of the influence of bed roughness on turbulent flow properties. For this purpose, an efficient, second order accurate 'immersed boundary method' was implemented into the LES code Hydro3d-GT, and validated for flow past bluff bodies. LES results from the present study showed excellent agreement with previous experimental studies on flow over rough beds. An in-depth analysis of time varying turbulent quantities (like the velocity fluctuations) revealed the presence of coherent structures in the flow. Also, a three dimensional visualization of the turbulent structures provided a good picture of the flow, especially in the near bed region, which is quite difficult to accomplish using experimental studies.

<p>A magnetostrictive material elongates when it is subjected to a magnetic field. This effect can then be used to design powerful actuators. The department of electromagnetic engineering has been working with magnetostricitve material and their applications since the 1980s and is presently engaged in a project focusing on magnetostrictive transducer utilisation for the aeronautic field.</p><p>The focus of the presented work has been to develop and improve methods and tools supporting the development of magnetostrictive actuators.</p><p>The axial-radial model was previously developed at the department and is well suited for circular cross sections of magnetostrictive rods. It is, however, common to laminate the magnetostrictive rods resulting in rectangular cross sections. The use of Cauer circuits allows modelling of the shielding effect. This shielding effect results in non-homogenous magnetisation and stress in both rectangular and circular cross sections of the rod. A model based on Cauer circuits, including a hysteresis model based on experimental data, was developed during the project. Furthermore, it is demonstrated how figures of merit and the use of finite element methods can be used to find optimised designs in a systematic and computational efficient way. The<i> modified generalised Fabry factor</i> <i>and the magnetisation inhomogeneity coefficient</i> are two proposed new figures of merit.</p><p>A Magnetostricitve material is characterised through an experimental procedure. Usually, magnetostrictive material exhibit large hysteresis. An important part of the material characterisation is the post-processing of the measurement data, including a de-hysterisation procedure. In the thesis, a de-hysterisation method which ensures energy consistent data is presented. Energy consistent material data is essential to achieve energy consistent simulations of magnetostrictive systems.</p><p>It is also demonstrated how the knowledge at the department can be utilised in international projects. In an ongoing project, the department is engaged in two sub tasks. In one of these sub tasks a high torque actuator is to be developed for the helicopter industry. The developed magnetostrictive models are used to perform system simulations of such actuator systems. In the other sub task a device for power harvesting from vibrations is analysed. It has now been shown how to adapt the load impedance in order to extract maximal electric power from the device.</p>

Flame based synthesis is a major manufacturing process of commercially valuable nanoparticles for large-scale production. However, this important industrial process has been advanced mostly by trial-and-error based evolutionary studies owing to the fact that it involves tightly coupled multiphysics flow phenomena. For large scale synthesis of nanoparticles, different physical and chemical processes exist, including turbulence, fuel combustion, precursor oxidation, and nanoparticle dynamics exist. A reliable and predictive computational model based on fundamental physics and chemistry can provide tremendous insight. Development of such comprehensive computational models faces challenges as they must provide accurate descriptions not only of the individual physical processes but also of the strongly coupled, nonlinear interactions among them. In this work, a multiscale computational model for flame synthesis of TiO2 nanoparticles in a turbulent flame reactor is presented. The model is based on the large-eddy simulation (LES) methodology and incorporates detailed gas phase combustion and precursor oxidation chemistry as well as a comprehensive nanoparticle evolution model. A flamelet-based model is used to model turbulence-chemistry interactions. In particular, the transformation of TiCl4 to the solid primary nucleating TiO2 nanoparticles is represented us- ing an unsteady kinetic model considering 30 species and 70 reactions in order to accurately describe the critical nanoparticle nucleation process. The evolution of the TiO2 number density function is tracked using the quadrature method of moments (QMOM) for univariate particle number density function and conditional quadrature method of moments (CQMOM) for bivariate density distribution function. For validation purposes, the detailed computational model is compared against experimental data obtained from a canonical flame- based titania synthesis configuration, and reasonable agreement is obtained. / text

This project examines the impact of Christian Science on American culture through the interventions of three major literary figures—Mark Twain, Willa Cather, and Theodore Dreiser—in the major debates that surrounded the movement. I argue that both Christian Science itself and the backlash against it were responses to the shifting conditions of modern life, that Christian Science and public discourse on it laid bare distinctly modern tensions and anxieties about changes in U.S. culture. Recent scholarship has pointed to the durability of the secularization thesis in the study of American literature despite the easily discernible impact of religion on American culture more broadly throughout the history of the U.S. This critical perspective has been particularly difficult to dismantle in the study of post-Civil War American literature. While it is true that Protestant Christianity lost some of its dominance in the late nineteenth century, this period also saw the rise of various influential heterodox religious groups, including Christian Science. This dissertation will make sense of why and how Christian Science captured the imaginations of so many Americans, including some of the greatest storytellers of the day. Christian Science was not the story of how a group of deluded fanatics attempted to turn back the tide of modernity. Instead, Christian Science was a product of modernity that provided a unique and, in its particular context, scientifically plausible response to the problem of human suffering. Furthermore, the controversies that surrounded Christian Science crystallized anxieties about the fate of individual autonomy in the modern U.S., the exercise of therapeutic and religious freedom, the concentration of individual wealth and power among a privileged few, the extension of American power abroad, and sexuality. Each chapter will examine a narrative or set of narratives that demonstrate how the Christian Science debates heightened and spoke to those concerns. / text

In the recent past, LES methodology has emerged as a viable tool for modeling turbulent combustion. LES computes the large scale mixing process accurately, thereby providing a better starting point for small-scale models that describe the combustion process. Significant effort has been made over past decades to improve accuracy and applicability of the LES approach to a wide range of flows, though the current conventions often lack consistency to the problems at hand. To this end, the two main objectives of this dissertation are to develop a dynamic transport equation-based combustion model for large- eddy simulation (LES) of turbulent spray combustion and to investigate grid- independent LES modeling for scalar mixing. Long-standing combustion modeling approaches have shown to be suc- cessful for a wide range of gas-phase flames, however, the assumptions required to derive these formulations are invalidated in the presence of liquid fuels and non-negligible evaporation rates. In the first part of this work, a novel ap- proach is developed to account for these evaporation effects and the resulting multi-regime combustion process. First, the mathematical formulation is de- rived and the numerical implementation in a low-Mach number computational solver is verified against one-dimensional and lab scale, both non-reacting and reacting spray-laden flows. In order to clarify the modeling requirements in LES for spray combustion applications, results from a suite of fully-resolved direct numerical simulations (DNS) of a spray laden planar jet flame are fil- tered at a range of length scales. LES results are then validated against two sets of experimental jet flames, one having a pilot and allowing for reduced chemistry modeling and the second requiring the use of detail chemistry with in situ tabulation to reduce the computational cost of the direct integration of a chemical mechanism. The conventional LES governing equations are derived from a low-pass filtering of the Navier-Stokes equations. In practice, the filter used to derive the LES governing equations is not formally defined and instead, it is assumed that the discretization of LES equations will implicitly act as a low-pass filter. The second part of this study investigates an alternative derivation of the LES governing equations that requires the formal definition of the filtering operator, known as explicitly filtered LES. It has been shown that decoupling the filter- ing operation from the underlying grid allows for the isolation of subfilter-scale modeling errors from numerical discretization errors. Specific to combustion modeling are the aggregate errors associated with modeling sub-filter distribu- tions of scalars that are transported by numerical impacted turbulent fields. Quantities of interest to commonly-used combustion models, including sub- filter scalar variance and filtered scalar dissipation rate, are investigated for both homogeneous and shear-driven turbulent mixing. / text

Extreme hydrological events associated with global warming are likely to produce an increasing number of flooding scenarios resulting in significant bridge inundation and associated damages. During large floods, the presence of a bridge in an open channel triggers a highly turbulent flow field including 3D complex coherent structures around bridge structures. These turbulence structures are highly energetic and possess high sediment entrainment capacity which increases scouring around the bridge foundation and consequently lead to structural stability problems or even failure of the structure. Hence, understanding the complex turbulent flow field for these extreme flow conditions is crucial to estimate the failure risks for existing bridges and better design of future bridges. This research employs the method Large Eddy Simulation (LES) to predict accurately the 3D turbulent flow around bridge structures. The LES code is refined with a novel free surface algorithm based on the Level Set Method (LSM) to determine the complex water surface profiles. The code is used to analyze the hydrodynamics of compound channel flow with deep and shallow overbanks, free flow around a bridge abutment, pressure flow with a partially submerged bridge deck and bridge overtopping flow. All simulations are validated with data from complementary physical model tests under analogous geometrical and flow conditions. Primary velocity, bed shear stress, turbulence characteristics and 3D coherent flow structures are examined thoroughly for each of the flow cases to explain the hydrodynamics of these complex turbulent flows.