Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2003. / In title on t.p., "[Beta]" appears as the Greek letter. / Includes bibliographical references (p. 81-84). / by Shinichiro Kida. / S.M.

A series of numerical modeling studies were conducted to characterize the mass flow rates in balcony spill plumes (BSP), a type of buoyant fire plume occurring in atria. The variation of BSP mass flow rate as a function of elevation, fire size and fire compartment geometry was examined both numerically and experimentally. A new method for estimation of BSP mass flow rates, appropriate for design of smoke management systems in high-elevation atria, was developed based on simulations of BSP mass flow rate. An experimental program conducted in a 12 m high atrium measured BSP mass flow rates as well as temperatures in the fire compartment and atrium. This data was used to evaluate CFD models of the fire compartment and atrium in the experimental facility. These were implemented using the Fire Dynamics Simulator (FDS) software. The models were extended to investigate BSP behaviour at elevations up to 50 m. The removal of atrium walls in the model to allow free development of the BSP is a unique approach among published numerical modeling studies of BSP behaviour. The high-elevation CFD model was used to perform a parametric study of BSP mass flow rate as a function of elevation, fire size and fire compartment geometry. Predictions of BSP mass flow rate from this study extend to 50 m above the atrium floor, extending the range of elevations represented in the published experimental data (<= 9 m). Data from the parametric study was used to develop a new method for estimation of BSP mass flow rates at high elevations. BSP mass flow rates estimated using the new method are shown to be bounded by values estimated using existing methods based on low-elevation experimental data.

A series of numerical modeling studies were conducted to characterize the mass flow rates in balcony spill plumes (BSP), a type of buoyant fire plume occurring in atria. The variation of BSP mass flow rate as a function of elevation, fire size and fire compartment geometry was examined both numerically and experimentally. A new method for estimation of BSP mass flow rates, appropriate for design of smoke management systems in high-elevation atria, was developed based on simulations of BSP mass flow rate. An experimental program conducted in a 12 m high atrium measured BSP mass flow rates as well as temperatures in the fire compartment and atrium. This data was used to evaluate CFD models of the fire compartment and atrium in the experimental facility. These were implemented using the Fire Dynamics Simulator (FDS) software. The models were extended to investigate BSP behaviour at elevations up to 50 m. The removal of atrium walls in the model to allow free development of the BSP is a unique approach among published numerical modeling studies of BSP behaviour. The high-elevation CFD model was used to perform a parametric study of BSP mass flow rate as a function of elevation, fire size and fire compartment geometry. Predictions of BSP mass flow rate from this study extend to 50 m above the atrium floor, extending the range of elevations represented in the published experimental data (<= 9 m). Data from the parametric study was used to develop a new method for estimation of BSP mass flow rates at high elevations. BSP mass flow rates estimated using the new method are shown to be bounded by values estimated using existing methods based on low-elevation experimental data.

Turbulent mixing enhancement has received a great deal of attention in the fluid mechanics community in the last few decades. Generally speaking, mixing enhancement involves the increased dispersion of the fluid that makes up a flow. The current work focuses on mixing enhancement of an axisymmetric jet via high amplitude fluidic pulses applied at the nozzle exit with high aspect ratio actuator nozzles. The work consists of small scale clean jet experiments, small scale micro-turbine engine experiments, and full scale laboratory simulated core exhaust experiments using actuators designed to fit within the engine nacelle of a full scale aircraft. The small scale clean jet experiments show that mixing enhancement compared to the unforced case is likely due to a combination of mechanisms. The first mechanism is the growth of shear layer instabilities, similar to that which occurs with an acoustically excited jet except that, in this case, the forcing is highly nonlinear. The result of the instability is a frequency bucket with an optimal forcing frequency. The second mechanism is the generation of counter rotating vortex pairs similar to those generated by mechanical tabs. The penetration depth determines the extent to which this mechanism acts. The importance of this mechanism is therefore a function of the pulsing amplitude. The key mixing parameters were found to be the actuator to jet momentum ratio (amplitude) and the pulsing frequency, where the optimal frequency depends on the amplitude. The importance of phase, offset, duty cycle, and geometric configuration were also explored. The experiments on the jet engine and full scale simulated core nozzle demonstrated that pulse fluidic mixing enhancement was effective on realistic flows. The same parameters that were important for the cleaner small scale experiments were found to be important for the more realistic cases as well. This suggests that the same mixing mechanisms are at work. Additional work was done to optimize, in real time, mixing on the small jet engine using an evolution strategy.

Volcanogenic lightning has a long documented history in the scientific field, though its origins are still poorly understood. The interactions leading to electrification of ash plumes is essentially a function of the microphysics controlling and affecting ash particle collisions. This thesis presents measurements made on charged particle interactions in a fluidized bed, with large-scale applications to the phenomenon of volcanogenic lightning and charged particle dynamics in volcanic plumes. Using a fluidized bed of ash samples taken from Ecuador's Volcán Tungurahua, particles are introduced to a collisional environment, where they acquire an associated polarity. A charged copper plate is used to collect particles of a given polarity, and particle size distributions are obtained for different weight fractions of the ash. It is observed that relatively smaller particles acquire a net negative charge, while larger particles in the sample charge positively. This is a well-documented occurrence with perfectly spherical, chemically identical samples, but this work represents one of the first applications of the principle to volcanic ash. Image analysis is preformed to determine the size distribution associated with specific polarities, and the associated minimum charge on each particle is calculated based on the plate collection height and particle size. We also present results that demonstrate the relationship between particle collisions and the amount of charge exchanged. Using techniques developed to examine the collision rate within a flow, combined with the charging rates determined from this experiment, we determine a maximum charge exchange rate of 1.28±0.23 electrons transferred per collision.

No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1986.

[pt] A questão da poluição ambiental está recebendo cada vez mais importância. Por esse motivo, os estudos relacionados a processos de dispersão de poluentes estão ganhando cada vez mais destaques. Como estudos em campo são mais custosos, os estudos realizados em laboratório, com modelos reduzidos, estão sendo mais aplicáveis, uma vez que permitem análises de problemas específicos. Este trabalho tem como objetivo realizar um estudo exploratório em um túnel de vento do comportamento de uma pluma emitida por uma chaminé, que permita modificações nas condições de velocidade e temperatura da pluma. Para isso, foi realizada a reprodução da camada limite atmosférica, através do Método de Irwin, simulando um ambiente suburbano, em que o perfil de velocidades média foi medido com a técnica de Anemometria de Fio Quente. Foram realizados ensaios para três condições do escoamento principal e levantados os perfis de velocidade e intensidade turbulenta à jusante da chaminé. Foi realizado um estudo da inclinação da pluma, tanto pela influência da velocidade, quanto pela diferença de temperatura da pluma em relação à do escoamento principal, que foi variada em 10 e 20 graus Celsius. As análises de concentração foram possíveis através das imagens obtidas com a técnica de Velocimetria por Imagem de Partículas. Foram feitas análises do perfil de concentração a diferentes posições a sotavento da chaminé e o coeficiente de dispersão vertical obtido foi comparado com diversas literaturas conhecidas. / [en] Environmental pollution issue is becoming increasingly important. For this reason, studies related to processes of atmospheric dispersion of pollutants are gaining prominence. Since studies in situ are expensive, laboratory studies with reduced models are useful, since specific problem can be investigated. The present work performs an experimental study, in a wind tunnel, evaluating the behavior of a plume generated by a chimney. For this, the reproduction of the atmospheric boundary layer was made, using the Irwin method, simulating a suburban environment, in which the mean velocity profile was measured with the Hot Wire Anemometry technique. Tests were performed for three main flow conditions and the profiles of velocity and turbulent intensity were made upstream of the stack. A study of the bent of the plume was made, both by the influence of the velocity, and by the temperature difference between the plume and the main flow, that was varied at 10 and 20 degrees Celsius. The concentration analyzes were possible through the images obtained with the Particle Image Velocimetry technique. Concentration profile analyzes were performed at different leeward positions of the chimney and the vertical dispersion coefficient obtained was compared with several known literatures.

La prédiction de l'émission infrarouge des jets de propulseurs composites aluminisés nécessite principalement trois étapes : le calcul des grandeurs aérothermochimiques du jet, la conversion de ces grandeurs en propriétés optiques (coefficient d'absorption, coefficient de diffusion, fonction de phase) puis la résolution de l'équation de transfert radiatif. Cette thèse,essentiellement consacrée à cette troisième étape, propose de nouvelles voies pour l'application des modèles de bande aux cas de milieux biphasiques et diffusants.D'une part, nous avons étendu ces modèles aux cas de milieux caractérisés par un déséquilibre thermique entre gaz et particules. D'autre part, nous avons proposé une méthode de séparation de la luminance en deux contributions, appelées respectivement non diffusée et diffusée, à partir d'une idée originale de Liu et al. La contribution non diffusée est solution de l'équation de transfert radiatif obtenue en ignorant les effets de la diffusion. Par conséquent, elle peut être résolue par une formulation en modèles de bande. Cette approche permet de réduire les erreurs de corrélations spectrales au seul terme de luminance diffusée.Nous avons montré l'intérêt de ces approches par comparaison avec une résolution de l'équation de transfert radiatif en raie par raie, sur des milieux représentatifs de situations de télédétection de jets. / Prediction of infrared emission of exhaust plumes from aluminized composite rocket, follows mainly three steps : calculating aero-thermo-chemical values in the plume, converting those valuesto optical properties (absorption coefficient, scattering coefficient and phase function) and resolving the radiative transfer equation. This thesis is mostly devoted to this third step, and proposes new ways to use band models on two-phases and scattering media.Firstly, we extended band models to cases with thermic non equilibrium between gas and particles. Secondly, we proposed a method consisting in splitting radiance in two parts, one called un-scattered and the other scattered, from an original idea of Liu et al. The un-scattered part is solution of the radiative transfer equation obtained by ignoring scattering. As a result, the unscattered radiance can be found by using band models. By this approach, errors on spectral correlations are only present on the scattered radiance.We show the interest of thoses approches by comparing them with a line by line resolutionof the radiative transfer equation, on media representative of remote sensing cases of rocket exhaust plumes.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2000. / "September 1999." / Includes bibliographical references. / Geochemical studies are fundamental for understanding how the dynamic Earth works and evolves. These studies place constraints on the composition, formation, age, distribution, evolution and scales of geochemically distinct reservoirs such as the Earth's crust, mantle and core. In this dissertation the strategy has been to work on a broad range of topics to evaluate crustal and mantle processes. This study presents Re-Os systematics to constrain the composition, formation and age of the lower continental crust and the mantle lithosphere, examines melt inclusion from oceanic island basalts to evaluate the scale of the mantle heterogeneities, and uses U-series isotope to constrain geodynamic parameters, such as the upwelling velocities and porosities of mantle plumes. The lower continental crust plays a pivotal role in understanding the composition and evolution of the continental crust and the petrogenesis of continental basalts. / by Alberto Edgardo Saal. / Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988. / Includes bibliographical references (p. 145-152). / by Sarah Alden Little. / Ph.D.