The understanding of the physics of the Coherent Structures and their interaction with the remaining fluid motions is of paramount interest in Turbulence Research. Indeed, recently had been suggested that separating and understanding the the different physical behavior of Coherent Structures and "uncoherent" background might very well be the key to understand and predict Turbulence. Available understanding of Coherent Structures shows that their size is considerably larger than the turbulent macro-scale, making permissible the application of Large Eddy Simulation to their simulation and study, with the advantage to be able to study their behavior at higher Re and more complex geometry than a Direct Numerical Simulation would normally allow. Original purpose of the present work was therefore the validation of the use of Large Eddy Simulation for the study of Coherent Structures in Shear-Layer and the its application to different flow cases to study the effect of the flow topology on the Coherent Structures nature. However, during the investigation of the presence of Coherent Structures in numerically generated LES flow fields, the aging in house Large Eddy Simulation (LES) code of the Environmental & Applied Fluid Dynamics Department has shown a series of limitations and shortcomings that led to the decision of relegating it to the status of Legacy Code (from now on indicated as VKI LES legacy code and of discontinuing its development. A new natively parallel LES solver has then been developed in the VKI Environmental & Applied Fluid Dynamics Department, where all the shortcomings of the legacy code have been addressed and modern software technologies have been adopted both for the solver and the surrounding infrastructure, delivering a complete framework based exclusively on Free and Open Source Software (FOSS ) to maximize portability and avoid any dependency from commercial products. The new parallel LES solver retains some basic characteristics of the old legacy code to provide continuity with the past (Finite Differences, Staggered Grid arrangement, Multi Domain technique, grid conformity across domains), but improve in almost all the remaining aspects: the flow can now have all the three directions of inhomogeneity, against the only two of the past, the pressure equation can be solved using a three point stencil for improved accuracy, and the viscous terms and convective terms can be computed using the Computer Algebra System Maxima, to derive discretized formulas in an automatic way. For the convective terms, High Resolution Central Schemes have been adapted to the three-dimensional Staggered Grid Arrangement from a collocated bi-dimensional one, and a system of Master-Slave simulations has been developed to run in parallel a Slave simulation (on 1 Processing Element) for generating the inlet data for the Master simulation (n - 1 Processing Elements). The code can perform Automatic Run-Time Load Balancing, Domain Auto-Partitioning, has embedded documentation (doxygen), has a CVS repository (version managing) for ease of use of new and old developers. As part of the new Frame Work, a set of Visual Programs have been provided for IBM Open Data eXplorer (OpenDX), a powerful FOSS Flow visualization and analysis tool, aimed as a replacement for the commercial TecplotTM, and a bug tracking mechanism via Bugzilla and cooperative forum resources (phpBB) for developers and users alike. The new M.i.O.m.a. (MiOma) Solver is ready to be used again for Coherent Structures analysis in the near future.

The developments of new technologies for commercial aviation involve significant risk for technologists as these programs are often driven by fixed assumptions regarding future airline needs, while being subject to many uncertainties at the technical and market levels. To prioritize these developments, technologists must assess their economic viability even though standard methods used for capital budgeting are not well suited to handle the overwhelming uncertainty surrounding such developments. This research proposes a framework featuring real options to overcome this challenge. It is motivated by three observations: disregarding the value of managerial flexibility undervalues long-term research and development (R&D) programs; windows of opportunities emerge and disappear and manufacturers can derive significant value by exploiting their upside potential; integrating competitive aspects early in the design ensures that development programs are robust with respect to moves by the competition. Real options analyses have been proposed to address some of these points but the adoption has been slow, hindered by constraining frameworks. A panel of academics and practitioners has identified a set of requirements, known as the Georgetown Challenge, that real options analyses must meet to get more traction amongst practitioners in the industry. In a bid to meet some of these requirements, this research proposes a novel methodology, cross-fertilizing techniques from financial engineering, actuarial sciences, and statistics to evaluate and study the timing of technology developments under uncertainty. It aims at substantiating decision making for R&D while having a wider domain of application and an improved ability to handle a complex reality compared to more traditional approaches. The method named FLexible AViation Investment Analysis (FLAVIA) uses first Monte Carlo techniques to simulate the evolution of uncertainties driving the value of technology developments. A non-parametric Esscher transform is then applied to perform a change of probability measure to express these evolutions under the equivalent martingale measure. A bootstrap technique is suggested next to construct new non-weighted evolutions of the technology development value under the new measure. A regression-based technique is finally used to analyze the technology development program and to discover trigger boundaries which help define when the technology development program should be launched. Verification of the method is performed on several canonical examples and indicates good accuracy and competitive execution time. It is applied next to the analysis of a performance improvement package (PIP) development using the Integrated Cost And Revenue Estimation method (i-CARE) developed as part of this research. The PIP can be retrofitted to currently operating turbofan engines in order to mitigate the impact of the aging process on their operating costs. The PIP is subject to market uncertainties, such as the evolution of jet-fuel prices and the possible taxation of carbon emissions. The profitability of the PIP development is investigated and the value of managerial flexibility and timing flexibility are highlighted.The developments of new technologies for commercial aviation involve significant risk for technologists as these programs are often driven by fixed assumptions regarding future airline needs, while being subject to many uncertainties at the technical and market levels. To prioritize these developments, technologists must assess their economic viability even though standard methods used for capital budgeting are not well suited to handle the overwhelming uncertainty surrounding such developments. This research proposes a framework featuring real options to overcome this challenge. It is motivated by three observations: disregarding the value of managerial flexibility undervalues long-term research and development (R&D) programs; windows of opportunities emerge and disappear and manufacturers can derive significant value by exploiting their upside potential; integrating competitive aspects early in the design ensures that development programs are robust with respect to moves by the competition. Real options analyses have been proposed to address some of these points but the adoption has been slow, hindered by constraining frameworks. A panel of academics and practitioners has identified a set of requirements, known as the Georgetown Challenge, that real options analyses must meet to get more traction amongst practitioners in the industry. In a bid to meet some of these requirements, this research proposes a novel methodology, cross-fertilizing techniques from financial engineering, actuarial sciences, and statistics to evaluate and study the timing of technology developments under uncertainty. It aims at substantiating decision making for R&D while having a wider domain of application and an improved ability to handle a complex reality compared to more traditional approaches. The method named FLexible AViation Investment Analysis (FLAVIA) uses first Monte Carlo techniques to simulate the evolution of uncertainties driving the value of technology developments. A non-parametric Esscher transform is then applied to perform a change of probability measure to express these evolutions under the equivalent martingale measure. A bootstrap technique is suggested next to construct new non-weighted evolutions of the technology development value under the new measure. A regression-based technique is finally used to analyze the technology development program and to discover trigger boundaries which help define when the technology development program should be launched. Verification of the method is performed on several canonical examples and indicates good accuracy and competitive execution time. It is applied next to the analysis of a performance improvement package (PIP) development using the Integrated Cost And Revenue Estimation method (i-CARE) developed as part of this research. The PIP can be retrofitted to currently operating turbofan engines in order to mitigate the impact of the aging process on their operating costs. The PIP is subject to market uncertainties, such as the evolution of jet-fuel prices and the possible taxation of carbon emissions. The profitability of the PIP development is investigated and the value of managerial flexibility and timing flexibility are highlighted.

Bostads- och arbetsmarknaden är två relevanta ämnen som ofta diskuteras i olika forum. Utifrån teorin om utbud och efterfrågan samt hedoniska prissättningsmodellen och utformad hypotes syftar studien till att finna ett kausalt samband av en negativ chock i efterfrågan på arbetskraft på bostadsmarknaden. Tidigare studier har gjorts på liknande ämnen, dock har ingen sådan studie med utgångspunkt i Sverige identifierats. Med hjälp av en staggered difference-in-differences-modell analyseras paneldata över sju svenska kommuner med målsättning att undersöka studiens syfte och frågeställning, där samtliga kommuner har exponerats för ett beslut om nedläggning av större arbetsplats. Modellens utfallsvariabel är slutpris per kvadratmeter och kontrollvariabler som inkluderas är olika hedoniska egenskaper för bostäder såsom boarea, antal rum och ägandeform, samt en indikatorvariabel för beslut om nedläggning. Likt tidigare utförda studier som studerar effekten av ökad arbetslöshet på bostadsmarknaden, visar studien på en negativ effekt. Konträrt till tidigare studier är effekten däremot ej statistiskt signifikant.

Microchannels have been studied extensively for electronic cooling applications ever since they were found to be effective in removing high heat flux from small areas. The rate of heat removed using microchannels depends on many factors including the geometry shape, solid and fluid materials used, and surface roughness, among others. Many configurations of microchannels have been studied with various materials and compared for their effectiveness in heat removal. However, there is little research done so far in using Phase Change Material (PCM) fluids and pin fins in microchannels to enhance the heat transfer. PCM fluids exhibit greater heat transfer when the phase change material undergoes liquid-to-solid transformation. Staggered pins in microchannels have also shown higher heat removal characteristics because of the continuous breaking and formation of the thermal and hydrodynamic boundary layer; they also exhibit higher pressure drop because pins act as flow obstructers. This paper presents numerical results of circular, square, straight rectangular microchannels with various aspect ratios (1:2, 1:4 and 1:8), and rectangular microchannels with two characteristic staggered pins (square and circular, fixed height with no variation in aspect ratio). The heat transfer performance of a single phase fluid and PCM fluid in all of these microchannels and the corresponding pressure drop characteristics are also presented. An effective specific heat capacity model was used to account for the phase change process of PCM fluid. Comparison of heat transfer characteristics of single phase fluid and PCM fluid are presented for all the geometries considered. Among the straight microchannels, 1:8 geometry was found to have the highest Nusselt number. The use of PCM fluid in straight microchannels increased the Nusselt number by 3-7 percent compared to the single phase fluids. Among the staggered pin microchannels, circular pins were found to be more effective in terms of heat transfer by exhibiting higher Nusselt number. Circular pin microchannels were also found to have lower pressure drop compared to the square pin microchannels. Overall, for all the geometries considered, it was found that the PCM fluid enhances the heat transfer compared to the SPF fluid.

Pattern geometry plays a major role in determining oil recovery during waterflooding and enhanced oil recovery operations. Although simulation is an important tool for design and evaluation, the first step often involves rough calculations based upon areal sweep efficiencies of displacements in homogeneous, two-dimensional, scaled, physical models. These results are available as a function of the displacement pattern and the mobility ratio M. In this research I studied the effect of mobility ratios on five-spot and staggered waterflood patterns behavior for areal (2D) displacement in a reservoir that is homogeneous and isotropic containing no initial gas saturation. Simulation was performed using Eclipse 100 simulator. Simulation results are presented as graphs of areal sweep efficiency at breakthrough versus Craig mobility ratio for various staggered line drive aspect ratios. The main results of the study are presented in the form of a graph of areal sweep efficiency at breakthrough as a function of staggered line drive aspect ratio. This should enable engineers to utilize the results in a convenient manner.

No description available.

We develop and analyse explicit in time schemes for the computation of compressible flows, based on staggered in space. Upwinding is performed equation by equation only with respect to the velocity. The pressure gradient is built as the transpose of the natural divergence. For the barotropic Euler equations, the velocity convection is built to obtain a discrete kinetic energy balance, with residual terms which are non-negative under a CFL condition. We then show that, in 1D, if a sequence of discrete solutions converges to some limit, then this limit is the weak entropy solution. For the full Euler equations, we choose to solve the internal energy balance since a discretization of the total energy is rather unnatural on staggered meshes. Under CFL-like conditions, the density and internal energy are kept positive, and the total energy cannot grow. To obtain correct weak solutions with shocks satisfying the Rankine-Hugoniot conditions, we establish a kinetic energy identity at the discrete level, then choose the source term of the internal energy equation to recover the total energy balance at the limit. More precisely speaking, we prove that in 1D, if we assume the L∞ and BV-stability and the convergence of the scheme, passing to the limit in the discrete kinetic and internal energy equations, we show that the limit of the sequence of solutions is a weak solution. Finally, we consider the computation of radial flows, governed by Euler equations in axisymetrical (2D) or spherical (3D) coordinates, and obtain similar results to the previous sections. In all chapters, we show numerical tests to illustrate for theoretical results. / We develop and analyse explicit in time schemes for the computation of compressible flows, based on staggered in space. Upwinding is performed equation by equation only with respect to the velocity. The pressure gradient is built as the transpose of the natural divergence. For the barotropic Euler equations, the velocity convection is built to obtain a discrete kinetic energy balance, with residual terms which are non-negative under a CFL condition. We then show that, in 1D, if a sequence of discrete solutions converges to some limit, then this limit is the weak entropy solution. For the full Euler equations, we choose to solve the internal energy balance since a discretization of the total energy is rather unnatural on staggered meshes. Under CFL-like conditions, the density and internal energy are kept positive, and the total energy cannot grow. To obtain correct weak solutions with shocks satisfying the Rankine-Hugoniot conditions, we establish a kinetic energy identity at the discrete level, then choose the source term of the internal energy equation to recover the total energy balance at the limit. More precisely speaking, we prove that in 1D, if we assume the L∞ and BV-stability and the convergence of the scheme, passing to the limit in the discrete kinetic and internal energy equations, we show that the limit of the sequence of solutions is a weak solution. Finally, we consider the computation of radial flows, governed by Euler equations in axisymetrical (2D) or spherical (3D) coordinates, and obtain similar results to the previous sections. In all chapters, we show numerical tests to illustrate for theoretical results.

The purpose of this study was to investigate the possibility of a familial lineage for dyslexia by analyzing certain auditory processing characteristics of dyslexic children and their parents. The Staggered Spondaic Word test was administered to twenty-one dyslexic children, eight to thirteen years of age, their natural parents and normal reading siblings. The experimental test data were tabulated and analyzed according to listening condition for each of the four groups: dyslexic children, normal reading siblings, affected parents and non-affected parents. A statistical analysis of the experimental data revealed significantly poorer Staggered Spondaic Word test performances for dyslexic children and their affected parents, in both the right and left competing listening conditions, when compared to test performances of their normal reading siblings and non-affected parents. These test results appear to support a genetic precursor theory for dyslexia. The experimental findings from the present investigation are discussed in terms of their clinical implications for the identification and management of dyslexic children.

The present study aims to explore dynamical behavior of the single cylinder and the staggered cylinder arrays in shear flow by numerical simulations. The results are compared with the case in uniform flow. After the observation of the fluid-elastic vibration in the staggered cylinder arrays in the two flows. This paper investigates the effects of the spacing(P/D), mass ratio and the shear parameter on the trajectories, oscillation amplitudes among the different cylinders. Continuity equation and momentum equations are used to solve the aforementioned problems alternatively by PISO method. Dynamic meshing techniques together with the cylinder motion equations are employed in the simulation. Under the different conditions, flow types and cylinder motion models, lock-in and fluid-elastic vibration are studied when the flow crosses the staggered cylinder arrays. The results show that the motion and the flow field around the single cylinder is consistent with the literature. In terms of the staggered cylinder arrays in uniform flow, the oscillation is dominated by the vortex shedding, and the lock-in area in the downstream cylinders is greater than the upstream cylinders. Fluid elastic vibration occurs in the small spacing between cylinders. In shear flow, when the shear parameters are larger or the spacing between cylinders are smaller, the more likely the fluid elastic vibration of the cylinders will occur.

Many technologically important problems are coupled in nature. For example, blood flow in deformable arteries, flow past (flexible) tall buildings, coupled deformation-diffusion, degradation, etc. It is, in general, not possible to solve these problems analytically, and one needs to resort to numerical solutions. An important ingredient of a numerical framework for solving these problems is the coupling algorithm, which couples individual solvers of the subsystems that form the coupled system, to obtain the coupled response. A popular coupling algorithm widely employed in numerical simulations of such coupled problems is the conventional staggered scheme (CSS). However, there is no systematic study on the stability characteristics of the CSS. The stability of coupling algorithms is of utmost importance, and assessment of the stability on real problems is not feasible given the computational costs involved. The main aim of this thesis, is to address this issue - assess the accuracy and stability characteristics of CSS using various canonical problems. In this thesis we show that the stability of CSS depends on the relative sizes of the domain, disparity in material properties, and the time step.