The concept of material dispersion is an important factor in analyzing the performance of an optical fiber system. The thesis presents an analysis of the material dispersion as a function of any pressure (in Mega Newton's per square meter) and temperature (in degrees Celsius). The pressure dependent and temperature dependent Sellmeier coefficients are considered for the analysis. The results obtained can be used in building a sensor that can be used for measuring dispersion as a function of pressure or temperature.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

Since a few years, nanomaterials are more and more used in industrial process. In order to protect the population and the environment from the consequences of an accidental release into the atmosphere, the risk assessment allowed to identify the accidental scenario in transport, manipulation and storage of those products. The accidental leakage of the conveying pipe may lead to a massive release of nanoparticles. In order to evaluate the consequences of this type of accident, our study focuses on the prediction of particles properties dispersed into the air, for example the particle number concentration and the particle diameter distribution. The first step of the study consists in the analyse of physical phenomena related to nanoparticles in order to choose the most predominant physical phenomena to model. The relevant physical phenomena in the present configuration are the agglomerate complex shape, the drag force on agglomerates, the agglomerate breakage by gas, the agglomerate collision and the agglomeration. After that, the modelling of physical phenomena chosen is developed in CFD tool Code\_Saturne. For each physical phenomenon, a simulation test case is realized in order to verify the development in CFD tool. A good agreement between CFD tool Code\_Saturne and 0D tool from Scilab and model in the literature is obtained. Also in the present study, new model for the collision probability of agglomerates is proposed. This new model is validated with the numerical experiment. After that, the numerical tool developed is applied in a simulation of an accidental pipe leakage. The field near the leakage is simulated by Code\_Saturne. The results from Code\_Saturne is used as the input data for ADMS tool, a simulation tool for the particle dispersion in large scale. The results show that the particles are dispersed more than 1 km from the release source, which is in agreement with the distance observed. In perspective, the influences of different parameters as the wind field and the particle properties, on the agglomerate size and number distribution can be tested. An experiment of the microparticle jet is realized at INERIS in order to be able to assess the nanoparticle jet experiment in the laboratory scale.

Over the previous summer I studied mixing of a passive tracer by flow in a straight cylindrical pipe, under the supervision of prof. Bernoff. The mixing process can be thought of as the successive action of advection by the fluid flow and diffusion modeled by random walks. With this method we were able to distinguish three different regimes. For short times, diffusion is more relevant than advection and we observed a Gaussian longitudinal distribution of the concentration. In an intermediate regime, advection by the shear is dominant over longitudinal diffusion and we observed a distinctively asymmetric distribution which spread much faster than would be expected by the action of diffusion alone. Finally when the tracer had completely mixed across the pipe’s cross- section, we recovered the classical Taylor regime with a longitudinal Gaussian distribution. In each regime we have analytical prediction of tracer distribution, confirmed by numerical calculation. The object of this thesis is to extend our results to curved pipes; we will start by considering curved planar pipes and helical pipes. We will try to determine if mixing in these geometries displays the same three distinctive regimes of mixing. The pipe’s curvature introduces a secondary flow in the form of a transverse recirculation with a dipolar form, discovered by Dean (1928). We believe this transverse flow should enhance mixing, which explains why curved pipes are used in cooling systems and other situations where heat exchange is relevant. Our object is to first understand existing analytical approximations to the flow in a curved pipe due to Dean and others and then to study analytically and numerically the spread of a passive scalar in these flows.

<p>Vi vill med denna uppsats undersöka vilka faktorer som styr prisspridningen på den svenska e-handelsmarknaden. De faktorer som studerats är produktens pris, popularitet, bransch, antal säljare och i vilken period som materialet samlats in. Undersökningen kom fram till resultatet att samtliga faktorer, förutom perioden för datainsamling, är statistiskt säkerställda på ett eller flera av våra prisspridningsmått. Det innebär att fyra av de fem faktorer som vi studerat påverkar prisspridningen.</p>

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Dennis W. Prather, Dept. of Electrical and Computer Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Vi vill med denna uppsats undersöka vilka faktorer som styr prisspridningen på den svenska e-handelsmarknaden. De faktorer som studerats är produktens pris, popularitet, bransch, antal säljare och i vilken period som materialet samlats in. Undersökningen kom fram till resultatet att samtliga faktorer, förutom perioden för datainsamling, är statistiskt säkerställda på ett eller flera av våra prisspridningsmått. Det innebär att fyra av de fem faktorer som vi studerat påverkar prisspridningen.

In this study the phenomenon of compressible flow and heat transfer in a porous media is modeled based on fundamental principles. The conservation equations for the two phases are transformed by the method of volume averaging which is an analytic method used to unite the microscale and macroscale effects characteristic to porous media flows. Unique to this analysis is that the model is valid for oscillatory, cryogenic flows such as that occurring in a regenerative cryogenic refrigerator such as a Pulse Tube Cryocooler (PTC.) In a PTC the forced flow drive oscillations in the regenerator create Reynolds numbers high enough such that microscale inertial effects dominate the momentum equation. This phenomenon, known as the Forchheimer Effect, can be predicted and modeled based solely on fundamental principles and the method of volume averaging. The coefficients that characterize the Forchheimer momentum equation are determined experimentally. In addition to pressure gradients, heat transfer within a porous media occurs due to temperature gradients. Conduction within the solid and fluid phases is made evident by volume averaging, but the determination of the conductivity coefficients requires numerical experiments and is unique to the geometry and conductivities of the two phases. Convection between the two phases is the dominant mode of heat transfer within the porous media. Determination of the convective heat transfer coefficient for a porous media requires physical experiments. Heat transfer and pressure gradients in the porous media are always competing effects leading to a model which requires coupling of the momentum and energy equations. These competing effects are united with the concept of entropy generation which relies on the second law of thermodynamics. All real processes generate entropy, and the most efficient processes which balance pressure gradients and heat transfer generate minimum entropy. This concept of minimum entropy generation is unique. As a result, minimum entropy generation should always be used as the criteria for thermodynamic optimization of thermohydraulic systems.