Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase. Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht. Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen. Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

This essay is written in order to better understand the relationship between the air around body (bubbles) and the external environment. Bubbles are explored as a mixture of feelings, emotions, imagination and thoughts, which we carry with us and which are formed by our perception of our environments. I will suggest that the formation of our bubbles is different at every moment, depending on how we feel about our external situation. Bubbles are used in the protection of ourselves, as the invisible wall that forms our territory. Within this essay I attempt to put forward the notion that we live in our own interpretations of our environments. Through a close analysis of my previous work, as well as through an analysis of two workshops that I was involved in, and through a close look at the work of the artist Cocky Eek, I aim to lay the ground for the way I will work with bubbles in my master project.

Coupled shape oscillations and translational motion of an incompressible gas bubble in a liquid container in response to forced vibration is studied numerically. Bond number (Bo) and the ratio of the vibration amplitude to the bubble diameter (A/D) are found to be the governing non-dimensional numbers. Bubble response is studied in both 2D and 3D. Different schemes are used for 2D and 3D simulations. In 2D, the flow solver is coupled to a Volume of Fluid (VOF) algorithm to capture the interface between the two phases while in 3D the interface is captured using a level set algorithm. The oscillation outcome ranges from small amplitude and regular oscillations for small Bo and A/D to large amplitude, nonlinear, and chaotic oscillations for large Bo and A/D. Chaotic behavior occurs due to the coupling between the nonlinear shape oscillations and large amplitude oscillatory translational motion. By further increase of the forcing, the inertia of the liquid results in the formation of a liquid jet which penetrates within the bubble core and pierces the bubble and a toroidal bubble shape is formed. The toroidal bubble shape then goes through large amplitude shape oscillations and smaller bubbles are formed. A summary of the 3D simulations provides a map which shows the bubble oscillation outcome as a function of Bo and A/D. The interaction between two bubbles is studied in 2D as well and the effect of vibration amplitude, frequency and liquid to gas density ratio on the interaction force is investigated.

Theories about ship wake structure, bubble dynamics, acoustic propagation through bubble clouds, backscattering and target strength of bubble clouds have been investigated and related Matlab simulations have been carried on. Research has been carried on algorithms for ship wake acoustic detection and tracking. Particle filter method has been simulated with Matlab for target tracking using wake echo measurements. Simulation results are promising.

Coupled shape oscillations and translational motion of an incompressible gas bubble in a liquid container in response to forced vibration is studied numerically. Bond number (Bo) and the ratio of the vibration amplitude to the bubble diameter (A/D) are found to be the governing non-dimensional numbers. Bubble response is studied in both 2D and 3D. Different schemes are used for 2D and 3D simulations. In 2D, the flow solver is coupled to a Volume of Fluid (VOF) algorithm to capture the interface between the two phases while in 3D the interface is captured using a level set algorithm. The oscillation outcome ranges from small amplitude and regular oscillations for small Bo and A/D to large amplitude, nonlinear, and chaotic oscillations for large Bo and A/D. Chaotic behavior occurs due to the coupling between the nonlinear shape oscillations and large amplitude oscillatory translational motion. By further increase of the forcing, the inertia of the liquid results in the formation of a liquid jet which penetrates within the bubble core and pierces the bubble and a toroidal bubble shape is formed. The toroidal bubble shape then goes through large amplitude shape oscillations and smaller bubbles are formed. A summary of the 3D simulations provides a map which shows the bubble oscillation outcome as a function of Bo and A/D. The interaction between two bubbles is studied in 2D as well and the effect of vibration amplitude, frequency and liquid to gas density ratio on the interaction force is investigated.

The flying-wing is a type of configuration which is a tailless airplane accommodating all of its parts within the outline of a single airfoil. Theoretically, it has the most aerodynamic efficiency. The fuel consumption can be more efficient than the existed conventional airliner. It seems that this configuration can achieve the above mentioned requirements. According to these outstanding advantages, many aircraft companies did a great deal of projects on the flying-wing concept. However, the application was only for sport and military use; for airliner, none of them entered production. FW-11 is a flying-wing configuration airliner which is a design cooperation between Cranfield University and Aviation Industry Corporation of China (AVIC). Aiming the spatial economic and environmental needs, this 200-seat airliner would attract attention from airline companies for cost saving and environmental protection. Before start, this program is designated for a new generation commercial aircraft to compete with the existing same capability airliner, such as Airbus A320 and Boeing 767. As the first team of this program, the aim is to finish the conceptual design and prepare the relevant document for next two teams that will perform preliminary and detail design. As a member of FW-11 program and as part of the GDP, the author has been through the four conceptual design stages: engine manufacturers, aircraft family issues, structure design and the establishment of 3-D CAD model. The aim of IRP study is to focus on the initial fuselage design.

Burbuchá will be a local, innovative and new concept located at the biggest private university in Central America where its students have an income between US$600 and US$1,200 providing a high quality product with locally produced and imported goods in order to provide the traditionally recognized Taiwanese drinks adjusted to the local taste. Burbuchá expects to open two kiosks during the first year at the two most important universities in the country and it also expects to penetrate 7% of the market by using among other strategies social media and vibrant promotions to foster trial and boost sales. Burbuchá will set a price below the ones of the coffee shops mainly because the main purpose is to increase the willingness of a market that is a coffee consumer to shift and try the tea based beverages. The initial investment required is US$ 61,390.00 which is going to be funded from the owner’s capital and a bank loan. Burbuchá kioks has a positive Net Present Value which indicates that the project is feasible. Burbuchá expects to expand to other markets in a period of 3 to 5 years through the franchise system. Its priority markets in the region are El Salvador, Costa Rica and Panama.

This thesis describes work on building numerical models of the Earth's magnetosphere using magnetohydrodynamics (MHD) and other related modeling methods. For many years, models that solve the MHD equations have been the main tool for improving our theoretical understanding of the large-scale dynamics of the Earth's magnetosphere. While the MHD models have been very successful in capturing many large-scale features, they fail to adequately represent the important drift physics in the inner magnetosphere. Consequently, the ring current, which contains most of the particle energy in the inner magnetosphere, is not realistically represented in MHD models. In this thesis, Chapter 2 and 3 will describe in detail our effort to couple the OpenGGCM (Open Geospace General Circulation Model), one of the major MHD models, to the Rice Convection Model (RCM), an inner magnetosphere ring current model, with the goal of including energy dependent drift physics into the MHD model. In Chapter 4, we will describe an initial attempt to use a direct-integration method to calculate Birkeland currents in the MHD code. Another focus of the thesis work, presented in Chapter 5, addresses a longstanding problem on how a geomagnetic substorm can occur within the closed field line region of the tail. We find a scenario of a bubble-blob pair formation in an OpenGGCM simulation just before the expansion phase of the substorm begins and the subsequent separation of the bubble and the blob decreases the normal component of the magnetic field until finally an X-line occurs. Thus the formation of the bubble-blob pair may play an important role in changing the magnetospheric configuration from a stretched field to the X-line formation that is believed to be the major signature of a substorm.

This research addresses a number of fundamental issues concerning convective mass transfer across fluid-fluid interfaces in porous media. Mass transfer to/from distributed sinks/sources is considered for i) the slow dissolution of liquid filaments of a wetting non-aqueous phase liquid (NAPL) held in the corners of angular pores or throats and ii) the fate of gas bubbles generated during the flow of a supersaturated aqueous phase in porous media. 1. Effects of the stability of NAPL films on wetting NAPL dissolution Wettability profoundly affects the distribution of residual NAPL contaminants in natural soils. Under conditions of preferential NAPL wettability, NAPL is retained within small pores and in the form of thick films (liquid filaments) along the corners and crevices of the pore walls. NAPL films in pore corners provide capillary continuity between NAPL-filled pores, dramatically influencing the behaviour of NAPL dissolution to the flowing aqueous phase by convection and diffusion. A pore network model is developed to explore the dissolution behaviour of wetting NAPL in porous media. The effects of initial NAPL distribution and NAPL film stability on dissolution behaviour are studied using the simulator. NAPL phase loses continuity and splits into disconnected clusters of NAPL-filled pores due to rupture of NAPL films. Quasi-state drainage and fingering of the aqueous phase into NAPL-filled pores is treated as an invasion percolation process and a stepwise procedure is adopted for the solution of flow and solute concentration fields. NAPL film stability is shown to critically affect the rate of mass transfer as such that stable NAPL films provide for more rapid dissolution. The network simulator reproduces the essential physics of wetting NAPL dissolution in porous media and explains the concentration-tailing behaviour observed in experiments, suggesting also new possibilities for experimental investigation. 2. Convective Mass Transfer across Fluid Interfaces in Straight Angular Pores Steady convective mass transfer to or from fluid interfaces in pores of angular cross-section is theoretically investigated. The model incorporates the essential physics of capillarity and solute mass transfer by convection and diffusion in corner fluid filaments. The geometry of the corner filaments, characterized by the fluid-fluid contact angle, the corner half-angle and the interface meniscus curvature, is accounted for. Boundary conditions of zero surface shear (‘perfect-slip’) and infinite surface shear (‘no-slip’) at the fluid-fluid interface are considered. The governing equations for laminar flow within the corner filament and convective diffusion to or from the fluid-fluid interface are solved using finite-element methods. Flow computations are verified by comparing the dimensionless resistance factor and hydraulic conductance of corner filaments against recent numerical solutions by Patzek and Kristensen [2001]. Novel results are obtained for the average effluent concentration as a function of flow geometry and pore-scale Peclet number. These results are correlated to a characteristic corner length and local pore-scale Peclet number using empirical equations appropriate for implementation in pore network models. Finally, a previously published “2D-slit” approximation to the problem at hand is checked and found to be in considerable error. 3. Bubble evolution driven by solute diffusion during the process of supersaturated carbonated water flooding In situ bubble growth in porous media is simulated using a pore network model that idealizes the pore space as a lattice of cubic chambers connected by square tubes. Evolution of the gas phase from nucleation sites is driven by the solute mass transfer from the flowing supersaturated water solution to the bubble clusters. Effects of viscous aqueous phase flow and convective diffusion in pore corners are explicitly accounted for. Growth of bubble clusters is characterised by a pattern of quasi-static drainage and fingering in the gas phase, an invasion percolation process controlled by capillary and gravitational forces. A stepwise solution procedure is followed to determine the aqueous flow field and the solute concentration field in the model by solving the conservation equations. Mobilization of bubbles driven by buoyancy forces is also studied. Results of bubble growth pattern, relative permeability and macroscopic mass transfer coefficient are obtained under different gas saturations and aqueous flow conditions.

Taiwanese stock market. The results suggest that there exist two heterogeneous agents in Taiwanese stock market, £\-investors behaving as long-term contrarian and £]-investor behaving as short-term momentum traders. To depict in detail the practical financial market, this research empirically tests HAM with different fundamental values (measured by the moving average price in different rolling windows) across different investment frequencies (daily, weekly and monthly). The result suggests that £\-investors (fundamentalists) expect prices to deviate from the short-term moving average but mean revert to long-term moving average. Beta investors (chartists) act as momentum traders in daily and monthly frequency, but short-term contrarian in weekly frequency. In addition, this study tests whether the parameters in HAM can explain some characteristics of crashes and bubbles. The result suggests that there are different investor behaviors in Asian, Dotcom, and Subprime crashes. By comparing the parameters (£\, £], and £^) of each individual stock, the study finds that stocks with contrarian £\-investors and short-term momentum £]-investors acting as short-term momentum traders have more volatile price pattern. As to crashes and individual stock volatility, the result suggests that sudden crashes (abrupt price decline) tend to occur in the stocks with short-term momentum traders, and while general crash (longterm economic cycle) tend to occur in the stocks with long-term contrarian investors. Stocks with larger Gamma, proxy for uncertainty, tends to have general crash only when £\-investors acting as contrarian and £]-investors acting as momentum traders.