Currently, the accurate prediction of the impact of an extreme wave on infrastructure located near shore is difficult to assess. There is a lack of established methods to accurately quantify these impacts. Extreme waves, such as tsunamis generate, through breaking, extremely powerful hydraulic bores that impact and significantly damage coastal structures and buildings located close to the shoreline. The damage induced by such hydraulic bores is often due to structural failure. Examples of devastating coastal disasters are the 2004 Indian Ocean Tsunami, 2005 Hurricane Katrina and most recently, the 2011 Tohoku Japan Tsunami. As a result, more advanced research is needed to estimate the magnitude of forces exerted on structures by such bores. This research presents results of a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method which is used to simulate the impact of extreme hydrodynamic forces on shore protection walls. Typically, fluids are modeled numerically based on a Lagrangian approach, an Eulerian approach or a combination of the two. Many of the common problems that arise from using more traditional techniques can be avoided through the use of SPH-based models. Such challenges include the model computational efficiency in terms of complexity of implementation. The SPH method allows water particles to be individually modeled, each with their own characteristics, which then accurately depicts the behavior and properties of the flow field. An open source code, known as SPHysics, was used to run the simulations presented in this thesis. Several cases analysed consist of hydraulic bores impacting a flat vertical wall as well as a sloping seawall. The analysis includes comparisons of the numerical results with published experimental data. The model is shown to accurately reproduce the formation of solitary waves as well as their propagation and breaking. The impacting bore profiles as well as the resulting pressures are also efficiently simulated using the model.

A three dimensional time-dependent coupled ecosystem model is applied to Izmir Bay for the first time. Delft3D modelling suite&rsquo / s FLOW and ECO modules are adapted and tuned for the region. A reference model with a time frame of three years is produced that represents the current physical and biogeochemical status of the bay. Model skill assessment methods are used as a measure of model performance and to address the shortcomings of it. The hydrodynamics model is able to produce physical features in terms of seasonality and spatial distribution within reasonable ranges, whereas the ecosystem model has certain discrepancies which can be reduced with improved quality of model inputs, such as open boundary conditions, and fresh water and nutrient fluxes. The reference model is used as a tool with predictive capacity to assess the ecosystem response of the bay to possible changes it may undergo in the future. Five nutrient enrichment/reduction scenarios are constructed to predict the reactions of the bay to changing external inputs of DIN and PO4. Results suggest that both physical and biogeochemical properties of the bay show strong horizontal gradients between outer and inner regions in which both natural and anthropogenic influences are effective. It is revealed that Outer bays are mostly occupied by waters originating from the oligotrophic Aegean Sea, while eutrophicated inner regions are mainly controlled by local influences such as increased fresh water inputs and excessive wastewater discharges. Results of the nutrient enrichment/reduction scenarios suggest that the N-limited Inner and Middle bays and the P-limited Outer bays, give contrasting reactions to changes in inputs of DIN and PO4 such that the former is more sensitive to DIN input whereas the latter is more sensitive to PO4 input. Due to the existence of these two contrasting environments in the bay, availability of one nutrient is dependent on the availability of the other, therefore treatment of both should be considered in parallel. Among the scenarios tested in this study, the best possible option to reduce eutrophication in Izmir Bay is to prevent the increase of PO4 input and to reduce the DIN input simultaneously. These outcomes are aimed to provide a scientific insight for coastal policy makers and environmental managers on how changes in anthropogenic influences can impact the marine ecosystem of the bay.

Classical nova explosions are stellar explosions that take place in close binary systems with an energy release only exceeded by gamma-ray bursts and supernova explosions. Matter from the white dwarf flows through the inner lagrangian point and spirals in towards the white dwarf for about 10^4-10^5 years, forming an accretion disk around it. Ultimately, part of this hydrogen-rich matter piles-up on top of the compact object and becomes partially degenerate due to the high densities attained. Consequently, temperature is allowed to rise, but the envelope does not experience any expansion. Actually, this is the key mechanism that controls the subsequent phases and powers a thermonuclear runaway, which is followed by an ejection of part of the accreted envelope. The ejecta are enriched with the products from the nuclear processes, presenting a final metallicity much above solar. This model, introduced in the early 70s, is a solid theory that can account for the gross scenario of nova explosions. Nevertheless, the theory relies on the fact that a mixing episode with matter from the white dwarf core has to take place at the core-envelope interface to successfully account for the high metallicities inferred from observations. During the past 40 years, theoreticians have performed many one-dimensional simulations, which can reproduce the abundances in the ejecta and other important observational properties. However, these calculations performed in spherical symmetry cannot study the mixing process, since they exclude a suite of very important multi-dimensional effects, such as convection. Therefore, multi-dimensional calculations are required to shed light into the mixing episode. In this thesis we have performed two- and three- dimensional simulations of CO novae to study the mixing mechanisms operating at the core-envelope interface, how convection sets in and how the deflagration spreads over the domain, by means of the Eulerian, parallelized, hydrodynamical FLASH code. The two-dimensional results show how convection sets in at the innermost envelope layers, after the appearance of temperature fluctuations that arise from the interface. Convection, in turn, powers the formation of kelvin-Helmholtz instabilities, which efficiently dredge-up 12C from the core and carry it into the envelope, reproducing correctly the high metallicity found in the ejecta. This result solves the controversy generated by the two existing two-dimensional calculations up-to-date. We have also realized a sensitivity study to analyze the impact of some initial parameters, such as the temperature perturbation, resolution of the simulations and the size of the computational domain. The results point out that these parameters have a negligible impact on the degree of mixing and, therefore, the calculations are not affected by numerical artifacts. Although two-dimensional calculations can quantitatively reproduce the mixing episode, they cannot describe correctly the convective pattern due to conservation of vorticity, which translates into recombination of the convective cells. Therefore, we have extended the work to three dimensions and performed the first three-dimesional model of mixing in classical novae up-to-date. These calculations can successfully reproduce the intermittency present in turbulent convection, with an energy cascade into smaller scales which clearly fulfills the Kolmogorov theory, while the thermonuclear runaway continues propagating with almost spherical symmetry. Mixing proceeds through the filamentary structure powered by robust kelvin-Helmholtz instabilitites that arise from the interface, resulting in a CNO enhancement which agrees with observations. This convective profile also generates density contrasts that could be the origin of the inhomogeneous distribution of chemical species. / Les explosions de noves tenen lloc en un sistema estel.lar binari, on un dels estels ha arribat a la fi de la seva vida convertit en una nana blanca. En sistemes binaris molt propers, l'estel acompanyant cedeix part del seu gas (material ric en hidrogen), el qual s'arremolina al voltant de la nana blanca durant prop de 10^4 - 10^5 anys. Una fracció d'aquest material acaba apilant-se a la superfície de l'objecte compacte i esdevé parcialment degenerat com a conseqüència de l'elevada densitat. Aquest fet és clau en el procés, ja que permet que la temperatura augmenti sense que es produeixi una expansió de l'embolcall, desencadenant un allau termonuclear i finalment, l'ejecció de matèria. El material ejectat està enriquit amb els isòtops processats en les reaccions nuclears, presentant una metal.licitat molt superior a la solar. Aquest model, presentat a principis dels anys 70, és una teoria sòlida que explica raonablement l'explosió de noves. No obstant, la teoria rau en el fet que s'ha de produir un procés de barreja entre el material de la nana blanca i el material de les capes més internes de l'embolcall per poder explicar l'alta metal.licitat que s'observa en el material ejectat. Durant els últims 40 anys, s'han fet molts estudis en una dimensió que aconsegueixen reproduir correctament les abundàncies del material ejectat i altres importants propietats observacionals, però que no poden explicar com es produeix el procés de barreja, ja que aquests càlculs amb simetria esfèrica exlouen tota una sèrie d'importants fenòmens multidimensionals. Per tant, per estudiar aquests aspectes de la teoria es requereixen estudis multidimensionals. En aquesta tesi hem realitzat simulacions en dues i tres dimensions de noves de CO per estudiar els mecanismes de barreja que es produeixen a la interfície del nucli de la nana blanca i l'embolcall, com s'estableix la convecció i com es propaga el front deflagratiu, mitjançant el codi hidrodinàmic FLASH, que és Eulerià i està paral.lelitzat. Els resultats en dues dimensions mostren com es genera convecció a les capes més internes de l'embolcall, després de la formació de fluctuacions de temperatura a la interfície. La convecció, al seu torn, origina inestabilitats Kelvin-Helmholtz que transporten eficientment 12C del nucli cap a l'embolcall, aconseguint reproduir correctament el grau de metal.licitat observat. Aquest resultat resol la controvèrsia generada pels dos estudis en dues dimensions realitzats fins ara. També hem realitzat un estudi per analitzar l'impacte dels paràmetres inicials tals com la perturbació inicial, la resolució de les simulacions o les dimensions del domini computacional. Els resultats indiquen que cap d'aquests paràmetres influeix en el grau de barreja final i, per tant, que els càlculs no estan condicionats per aspectes numèrics. Finalment, hem presentat el primer model tridimensional de barreja de noves fet fins ara. Aquest càlcul és necessari, ja que les simulacions bidimensionals, tot i que quantitativament reprodueixen la barreja esperada, no poden representar el patró convectiu correctament, degut a la conservació de la vorticitat, fent que les cel.les convectives esdevinguin cada cop més grans. El nostre càlcul aconsegueix reproduir el comportament intermitent de la turbulència, amb una cascada d'energia que flueix cap a escales cada cop més petites, tal i com prediu la teoria de Kolmogorov, alhora que el front convectiu avança pràcticament amb simetria esfèrica. La barreja procedeix a través de l'estructura filamentosa originada per l'aparició de potents inestabilitats Kelvin-Helmholtz a la interfície, obtenint-se una metal.licitat final a l'embolcall que concorda amb els valors observacionals. Aquest patró convectiu també genera contrastos de densitat que podrien ser l'origen de la distribució inhomogènia que presenten les espècies químiques.

A two-dimensional axisymmetric implementation of the smoothed particle hydrodynamics (SPH) technique, called for short AxisSPH, has been described in this thesis, along with a number of basic tests and realistic applications. The main goal of this work was to fill a gap on a topic which has been scarcely addressed in the published literature concerning SPH. Although the application of AxisSPH to the simulation of real problems is restricted to those systems which display the appropriate symmetry there are, however, many interesting examples of physical systems which evolve following the axisymmetric premise. These examples belong to a variety of scientific and technological areas such as, for example, astrophysics, laboratory astrophysics or inertial confinement fusion. Additionally AxisSPH can be also useful in convergence studies of the standard 3D-SPH technique because the higher resolution achieved in 2D can be used to benchmark the three-dimensional codes. The main improvements implemented in AxisSPH with respect existing axisymmetric SPH formulations are summarized as follows: 1) We have derived simple analytical expressions for correction factors which largely improves the calculation of density and velocity in the vicinity of the z-axis. These expressions and their derivatives were given as a function of an adimensional parameter and do not increase the computational load of the scheme. 2) We have obtained the appropriate expression of the fluid Euler equations containing the new correction functions and their derivatives. Far enough from the singular axis, the scheme reduces to the standard formulation discussed by Brookshaw (2003). 3) A novel expression for the heat conduction term, which has to be added to the energy equation was devised and checked. This new term improves the description of the heat flux for those particles located at the axis neighborhoods. 4) Until now axisymmetric SPH hydrocodes handle artificial viscosity using a crude approach because it was treated as a simple restriction of the standard 3D Cartesian viscosity to 2D. Here we propose to calculate the viscous pressure as a combination of two terms, the first one is the (standard) Cartesian part and the second is the axis-converging part of the viscosity respectively. As expected this last term is of special relevance to simulate implosions. 5) We have developed an original method to incorporate gravity into AxisSPH. First the direct ring to ring force was found as a function of the Euclidean distance between the 2D particles. In second place the gravitational force on a given particle was obtained by summing the contributions of all N particles. We have also developed a more efficient scheme to obtain the gravitational force calculating the potential of the ring, instead the force because it involves lesser algebraic operations. The scheme has been checked using a large number of tests cases. These tests range from very specific oriented to check a particular algorithm or a piece of physics, to rather complex ones intended to analyze the behavior of the scheme in potential real applications (ICF, jets, astrophysics). At least in one case, the head on collision of a pair of white dwarfs, the result of the simulations carried out using AxisSPH brings new, unpublished, scientific material. / En esta tesis se ha desarrollado un código, que hemos llamado AxisSPH, en dos dimensiones axisimétrico a partir de la técnica conocida como SPH (“smooothed particle hydrodynamics”). AxisSPH ha sido validado después de realizar una serie de tests básicos y algunas simulaciones de situaciones reales. El objetivo principal de este trabajo ha sido llenar, en parte, el vacío existente al respecto en la literatura sobre SPH. Aunque sólo se puede aplicar AxisSPH en problemas reales que presenten la apropiada simetría, existen muchos ejemplos interesantes de sistemas físicos que presentan la simetría axial demandada. Existen ejemplos en campos de aplicación tanto científica como tecnológica, por ejemplo en astrofísica, en el llamado laboratorio de astrofísica o en fusión por confinamiento inercial (ICF). Otra interesante aplicación de AxisSPH puede ser su utilización en estudios de convergencia con otros códigos 3D-SPH debido a su mayor resolución, al tratarse de un código 2D. Las mejoras implementadas en el código AxisSPH en comparación con otros códigos axisimétricos SPH existentes se pueden resumir en los siguientes puntos: 1) Hemos deducido expresiones analíticas simples para unos factores de corrección que mejoran el cálculo de la densidad y la velocidad en las proximidades del eje z. Dichas expresiones y sus derivadas dependen de un parámetro adimensional que no incrementa mucho el peso computacional del esquema propuesto. 2) Hemos obtenido las expresiones adecuadas de las ecuaciones de Euler que contienen estas nuevas funciones correctoras y sus derivadas. Lejos del eje de singularidad estas ecuaciones se transforman en las de la formulación estándar propuesta por Brookshaw (2003). 3) Una expresión novedosa del término de conducción, que debe de añadirse a la ecuación de la energía, se ha propuesto y validado. Este nuevo término mejora la evolución del flujo de calor de las partículas situadas en las proximidades del eje z. 4) Hasta el momento los códigos hidrodinámicos SPH axisimétricos existentes trabajaban con una aproximación poco elaborada de la viscosidad artificial ya que consistían en una restricción a dos dimensiones de la viscosidad estándar 3D. En este trabajo proponemos el cálculo de la presión debida a la viscosidad como combinación de dos términos, el primero reflejo de la parte cartesiana y la segunda da cuenta de la parte relacionada con la convergencia en el eje. Como era de esperar este último término es de relevante importancia en la simulación de implosiones. 5) Hemos desarrollado un método original para incorporar el cálculo de la gravedad en el código AxisSPH. En primer lugar la fuerza directa de anillo a anillo y en segundo lugar la fuerza de la gravedad que sufre una determinada partícula a partir de la contribución del resto de las N partículas existentes. También hemos desarrollado un esquema más eficiente para calcular la gravedad a partir del cálculo del potencial del anillo en lugar del cálculo directo de la fuerza ya que implica un menor número de operaciones algebraicas. El método ha sido verificado con un gran número de test numéricos. Desde los más específicos orientados a comprobar la validez de un algoritmo particular o la capacidad para simular un fenómeno físico en particular, hasta simulaciones bastante más complejas, con la intención de validar la capacidad de simular aplicaciones potencialmente más reales (ICF, jets, astrofísica). Así, en al menos un caso, en la colisión frontal de dos enanas blancas, los resultados de la simulación utilizando AxisSPH pueden aportar material científico publicable.

<p>The intent of the work discussed in this dissertation is to apply the engineering methods of theory/modeling, numerics/computation, and experimentation to a diverse assemblage of projects. Several projects are discussed: probabilistic modeling of decompression sickness, comparative hydrodynamics of cetacean flippers, optimization of CT/MRI protocols, evaluation of modified catheters, rudder cavitation, and modeling of mass transfer in amphibian cone outer segments. </p><p>The first project discussed is the probabilistic modeling of decompression sickness (DCS). This project involved developing a system for evaluating the success of decompression models in predicting DCS probability from empirical data. Model parameters were estimated using maximum likelihood techniques, and exact integrals of risk functions and tissue kinetics transition times were derived. Agreement with previously published results was excellent including maximum likelihood values within one log-likelihood unit of previous results and improvements by re-optimization, mean predicted DCS incidents within 1.4% of observed DCS, and time of DCS occurrence prediction. Alternative optimization and homogeneous parallel processing techniques yielded faster model optimization times. The next portion of this project involved investigating the nature and utility of marginal decompression sickness (DCS) events in fitting probabilistic decompression models to experimental dive trial data. Three null models were developed and compared to a known decompression model that was optimized on dive trial data containing only marginal DCS and no-DCS events. It was found that although marginal DCS events are related to exposure to decompression, empirical dive data containing marginal and full DCS outcomes are not combinable under a single DCS model; therefore, marginal DCS should be counted as no-DCS events when optimizing probabilistic DCS models with binomial likelihood functions. The final portion of this project involved the exploration of a multinomial DCS model. Two separate models based on the exponential-exponential/linear-exponential framework were developed: a trinomial model, which is able to predict the probabilities of mild, serious and no-DCS simultaneously, and a tetranomial model, which is able to predict the probabilities of mild, serious, marginal and no-DCS simultaneously. The trinomial DCS model was found to be qualitatively better than the tetranomial model, for reasons found earlier concerning the utility of marginal DCS events in DCS modeling. </p><p>The next project discussed is comparative hydrodynamics of cetacean flippers. Cetacean flippers may be viewed as being analogous to modern engineered hydrofoils, which have hydrodynamic properties such as lift coefficient, drag coefficient and associated efficiency. The hydrodynamics of cetacean flippers have not previously been rigorously examined and thus their performance properties are unknown. By conducting water tunnel testing using scale models of cetacean flippers derived via computed tomography (CT) scans, as well as computational fluid dynamic (CFD) simulations, a baseline work is presented to describe the hydrodynamic properties of several cetacean flippers. It was found that flippers of similar planform shape had similar hydrodynamic performance properties. Furthermore, one group of flippers of planform shape similar to modern swept wings was found to have lift coefficients that increased with angle of attack nonlinearly, which was caused by the onset of vortex-dominated lift. Drag coefficient versus angle of attack curves were found to be less dependent on planform shape. Larger cetacean flippers were found to have degraded performance at a Re of 250,000 compared to flippers of smaller odontocetes, while performance of larger and smaller cetacean flippers was similar at a swim speed of 2 m/s. Idealization of the planforms of cetacean flippers was found to capture the relevant hydrodynamic effects of the real flippers, although unintended consequences such as the lift curve slope changing from linear to nonlinear were sometimes observed. A numerical study of an idealized model of the humpback whale flipper showed that the leading-edge tubercles delay stall compared to a baseline (no tubercle) flipper because larger portions of the flow remaining attached at higher angles of attack. </p><p>The third project discussed is optimization of CT/MRI protocols. In order to optimize contrast material administration protocols for Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), a custom-built physiologic flow phantom was constructed to model flow in the human body. This flow phantom was used to evaluate the effect of varying volumes, rates, and types of contrast material, use of a saline chase, and cardiac output on aortic enhancement characteristics. For CT, reducing the volume of contrast material decreased duration peak enhancement and reduced the maximum value of peak enhancement. Increasing the rate of contrast media administration increased peak enhancement and decreased duration of peak enhancement. Use of a saline chase resulted in an increase in peak enhancement. Peak aortic enhancement increased when reduced cardiac output was simulated. For MRI, when the same volume of contrast material was injected at the same rate, the type of contrast material used has a significant effect on the greatest peak signal intensity and duration peak signal intensity. A higher injection rate of saline chaser is more advantageous than a larger volume of saline chaser to increase the peak aortic signal intensity using low contrast material doses. Furthermore, for higher volumes of contrast material, the effect of increasing the volume of saline chaser makes almost no difference while increasing the rate of injection makes a significant difference. When a saline chaser with a high injection rate is used, the dose of the contrast material may be reduced by 25-50% and more than 86% of the non-reduced dose peak aortic enhancement will be attained.</p><p>The next project discussed is evaluation of modified angiocatheters. In this study, a standard peripheral end hole angiocatheter was compared to those modified with side holes or side slits by using experimental techniques to qualitatively compare the contrast material exit jets, and by using numeric techniques to provide flow visualization and quantitative comparisons. A Schlieren imaging system was used to visualize the angiocatheter exit jet fluid dynamics at two different flow rates, and a commercial computational fluid dynamics (CFD) package was used to calculate numeric results for various catheter orientations and vessel diameters. Experimental images showed that modifying standard peripheral intravenous angiocatheters with side holes or side slits qualitatively changed the overall flow field and caused the exiting jet to become less well-defined. Numeric calculations showed that the addition of side holes or slits resulted in a 9-30% reduction of the velocity of contrast material exiting the end hole of the angiocatheter. With the catheter tip directed obliquely to the wall, the maximum wall shear stress was always highest for the unmodified catheter and always lowest for the 4 side slit catheter. Modified angiocatheters may have the potential to reduce extravasation events in patients by reducing vessel wall shear stress. </p><p>The next project discussed involves studying the effect of leading-edge tubercles on cavitation characteristics for marine rudders. Three different rudders were constructed and tested in a water tunnel: baseline, 3-tubercle leading edge, and 5-tubercle leading edge. In the linear (non-stall) regime, tubercled rudders performed equally to the smooth rudder. Hydrodynamic stall occurred at smaller angles of attack for the tubercled rudders than for the smooth rudder. When stall did occur, it was more gradual for the tubercled rudders, whereas the smooth rudder demonstrated a more dramatic loss of lift. At lower Re, the tubercled rudders also maintained a higher value of lift post-stall than the smooth rudder. Cavitation onset for the tubercled rudders occurred at lower angles of attack and higher values of cavitation number than for the smooth rudder, but cavities on the tubercled rudders were localized in the slots as opposed to the smooth rudder where the cavity spread across the entire leading edge. </p><p>In the final project discussed, modeling of mass transfer in amphibian cone outer segments, a detailed derivation of a simplified (continuum, one-dimensional) mathematical model for the radio-labeled opsin density profile in the amphibian cone outer segment is presented. This model relies on only one free parameter, which was the mass transfer coefficient between the plasmalemma and disc region. The descriptive equations were nondimensionalized, and scale analysis showed that advective effects could be neglected as a first approximation for early times so that a simplified system could be obtained. Through numeric computation the solution behavior was found to have three distinct stages. The first stage was marked by diffusion in the plasmalemma and no mass transfer in the disc region. The second stage first involved the plasmalemma reaching a metastable state whereas the disc region density increased, then involved both the plasmalemma and disc regions increasing in density with their distributions being qualitatively the same. The final stage involved a slow relaxation to the steady-state solution.</p> / Dissertation

<p>Locomotion in any environment requires the use of energy to overcome the physical</p><p>forces inherent in the environment. Most large marine vertebrates have evolved</p><p>streamlined fusiform body shapes to minimize the resistive force of drag when in</p><p>a neutral position, but nearly all behaviors result in some increase in that force.</p><p>Too much energy devoted to locomotion may reduce the available surplus necessary</p><p>for population-level factors such as reproduction. The population of North Atlantic</p><p>right whales has not recovered following legal protection due to decreased fecundity,</p><p>including an increase in the intercalf interval, an increase in the years to first calf and</p><p>an increase in the number of nulliparous females in the population. This reproductive</p><p>impairment appears to be related to deficiencies in storing enough energy to meet the</p><p>costs of reproduction. The goal of this study was to determine whether increases in</p><p>moving between prey patches at the cost of decreased foraging opportunities could</p><p>shift these whales into a situation of negative energy gain. The first step is to</p><p>understand the locomotor costs for this species for the key behaviors of traveling and</p><p>foraging.</p><p>This study investigated the cost of locomotion in right whales by recording the</p><p>submerged diving behaviors of free-ranging individuals in both their foraging habitat</p><p>in the Bay of Fundy and their calving grounds in the South Atlantic Bight with a</p><p>suction-cupped archival tag. The data from the tags were used to quantify the oc-</p><p>currence of different behaviors and their associated swimming behaviors and explore</p><p>three behavioral strategies that reduce locomotor costs. First, the influence that</p><p>changes in blubber thickness has on the buoyancy of these whales was investigated</p><p>by comparing the descent and ascent glide durations of individual whales with differ-</p><p>ent blubber thicknesses. Next, the depth of surface dives made by animals of different</p><p>sizes was related to the depth where additional wave drag is generated. Finally, the</p><p>use of intermittent locomotion during foraging was investigated to understand how</p><p>much energy is saved by using this gait. The final piece in this study was to deter-</p><p>mine the drag related to traveling and foraging behaviors from glides recorded by</p><p>the tags and from two different numerical simulations of flow around whales. One, a</p><p>custom developed algorithm for multiphase flow, was used to determine the relative</p><p>drag, while a second commercial package was used to determine the absolute mag-</p><p>nitude of the drag force on the simplest model, the traveling animal. The resulting</p><p>drag estimates were then used in a series of theoretical models that estimated the</p><p>energetic profit remaining after shifts in the occurrence of traveling and searching</p><p>behaviors.</p><p>The diving behavior of right whales can be classified into three stereotyped be-</p><p>haviors that are characterized by differences in the time spent in different parts of the</p><p>water column. The time budgets and swimming movements during these behaviors</p><p>matched those in other species, enabling the dive shapes to be classified as foraging,</p><p>searching and traveling behaviors. Right whales with thicker blubber layers were</p><p>found to perform longer ascent glides and shorter descent glides than those with</p><p>thinner blubber layers, consistent with the hypothesis that positive buoyancy does</p><p>influence their vertical diving behavior. During horizontal traveling, whales made</p><p>shallow dives to depths that were slightly deeper than those that would cause ad-</p><p>ditional costs due to wave drag. These dives appear to allow whales to both avoid</p><p>the costs of diving as well as the costs of swimming near the surface. Next, whales</p><p>were found to glide for 12% of the bottom phases of their foraging dives, and the</p><p>use of `stroke-glide' swimming did not prolong foraging duration from that used by</p><p>continuous swimmers. Drag coefficients estimated from these glides had an average</p><p>of 0.014 during foraging dives and 0.0052 during traveling, values which fall in the</p><p>range of those reported for other marine mammals. One numerical simulation deter-</p><p>mined drag forces to be comparable, while the other drastically underestimated the</p><p>drag of all behaviors. Finally, alterations to the behavioral budgets of these animals</p><p>demonstrated their cost of locomotion constitutes a small portion (8-12%) of the</p><p>total energy consumed and only extreme increases in traveling time could result in a</p><p>negative energy balance. In summary, these results show that locomotor costs are no</p><p>more expensive in this species than those of other cetaceans and that when removed</p><p>from all the other stressors on this population, these whales are not on an energetic</p><p>`knife edge'.</p> / Dissertation

An elastohydrodynamic analysis of a rotary lip seal is performed numerically, incorporating both the fluid mechanics of the lubricating film and the elastic deformation of the lip, by solving the Reynolds equation with flow factors. Asperities on the lip surface dominate the behavior of the flow field in the lubricating film and the elastic deformation of the lip. Since previous analyses treated those asperities deterministically, they required very large computation times. The present approach is much less computationally intensive because the asperities are treated statistically. Since cavitation and asperity orientation play important roles, these are taken into account in the computation of the flow factors. An asperity distortion analysis is introduced to obtain a more realistic model of the complex variations in the asperity distribution on the surface of the seal. Results of the analysis show how the operating parameters of the seal and the characteristics of the asperities affect such seal characteristics as the thickness of the lubricating film, reverse pumping rate, power dissipation and load carrying capacity.

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This document contains a proposal for the creation of a simulator that can accurately model the interaction of electromagnetic (EM) and semiconductor effects for modern wireless devices including nonlinear and/or active devices. The proposed simulator couples the balanced semiconductor equations (charge, momentum, kinetic energy) with a FDTD full-wave Yee-based electromagnetic (EM) simulator. The resultant CAD tool is able to model the response of one semiconductor device to both small signal and DC bias based on the process parameters (material, charge distribution and doping) without any a-priori knowledge of the device performance characteristics, thus making it extremely useful in modeling and integrating novel devices in RF and Wireless topologies. As a proof of concept an n+--i--n+ diode will be simulated. In the future, more complicated structures, such as MODFETs, will be modeled as well.

Mixing is a crucial process for many large scale and small scale applications from food industry to cosmetics, from drug industry to petrochemical processes, etc. Changes in parameters (temperature, viscosity, velocity distribution, etc.) during the mixing affect the production process and the end product quality and the cost. Thus, these parameters, mostly the hydrodynamic parameters, should be monitored closely during the process. In order to ensure good and efficient mixing in the solution, high degree of turbulence is maintained while dead zones in the tank should be avoided. In chemical industry, the mixing processes generally involve complex solutions that exhibit non-Newtonian flow behavior that merits a study on the agitation hydrodynamics and mixing time. Thus, in this study agitation of carboxymethyl cellulose (CMC) solution in a laboratory scale mixing tank is investigated. The effects of CMC concentration and agitation speed on the hydrodynamics of the solution and mixing time are studied in detail. CMC concentrations studied are 0.5 wt%, 1 wt% and 2 wt%. Impeller speeds, on the other hand, are set as 150 rpm, 300 rpm and 600 rpm. The hydrodynamics of mixing can be studied easily by Ultrasound Doppler Velocimetry (UDV) which is a fast, non-invasive measuring technique in fluid dynamics. Also, the mixing time measurements were carried out through electrical conductivity of the agitated solution. UDV results show that the flow field has a typical pattern produced by the Rushton turbine. The main characteristics of the flow are that, in the impeller region radial components of the flow dominate. Near the wall flow occurs mainly in the axial direction towards the top and bottom of the tank. Mixing time measurements reveal that mixing time increases with decreasing impeller speed and with increasing solution concentration (i.e. viscosity). Typical mixing time values are in the range of 250-2600 seconds for different impeller speeds and CMC concentrations.