There is a long terms of developement for academics theoretical analyzing and experimental researching by using the Lagrangian method. But for such trajectory experimentalists still have interference with reflected waves because of the length of the water tank is too short or the diameter and the density of the simulate particle , in spite of measuring the trajectory of the fluid particle have done. For there is no quite completed quantification data for the trajectory of fluid particle, this study is aiming at researching the truly movement of the flow field under wave-current interaction by trajectory measuring. This research choosing the simulate particle¡¦s diameter for 1 mm , collocating with a high-speed vedio camera to record the particle¡¦s moving characteristics while the wave-current interaction occured, to proceed a series of qualitative and quantitative testing. And to comple with all these data and improve the modification by using Image Processing to derive and orientate the coordinates . According to the experimental results of the flow field,it has proved that mass transport occured at the same-depth and no-flow condition through the wave progressing direction.The trajectory of the fluid particle of wave-current interaction in co-flow , its curve presenting the cross-convolution increasing and even presenting the cuspidal locus. And the trajectory of the fluid particle of wave-current interaction in inverse ¡Vflow is opposite to the trajectory of the no-flow movement. The results of the experiment is quite accord with to the 3rd order the theoretical analyzing of Chen ¡]1994¡^and Shu¡BChen¡]2006¡^¡CThe fluid particle reproducting the moving period of the high-elevation is greater than the wave¡¦s and increasing by the sharpness of the wave. The mass transport velocity is the same theory results ,and decreased deviation of artificiality in estimating particle position. According to the ratio of the experimental results, root mean square of error Ex and total mass transport displacement. The experimental results compared to the theoretical results obtained by Chen (1994)and Hsu¡BChen(2006) has the similar results as well.

Fuel cells are promising energy conversion devices, but they have not been widely adopted because of their very high cost. The most expensive component of a fuel cell is the membrane electrode assembly, a polymer film coated with catalyst material. The catalyst layer is fabricated by depositing and drying a liquid ink on the membrane. The membrane can rapidly absorb water from the ink, causing swelling strain sufficient for wrinkling, which can cause defects in the finished product. These challenges limit most catalyst layer fabrication to individual preparation by hand. We seek to understand the swelling phenomenon in a way that enables the control of defects during mass production. Membrane swelling is a transient, three-dimensional, coupled mass transfer, heat transfer and solid mechanics problem. Existing models describe the membrane in fuel cell operating conditions, making use of simplifying assumptions that are not valid for predicting manufacturing defects. We present a new model incorporating effects that are missing from other models. We present simulation results for scenarios relevant to the control of defects. Simple spatial variations in water content can cause curl and wrinkling; we establish criteria for the formation of these defects by simulating the membrane's response when subjected to the full pre-swollen coating and drying process. We investigate the sensitivity of wrinkling to nonuniformity in the coating and to processing conditions in the coating line. We propose a rationale for controlling wrinkling caused by these effects and for diagnosing coating defects using the membrane's wrinkling response. We show how the membrane behaves differently depending on whether the coating is applied to one side or to both sides simultaneously. We have designed and constructed a machine to pre-swell the membrane, apply a coating and then dry the coating under controlled tension, speed, temperature and humidity. We present the design and discuss how the machine may be used, together with the membrane model, to predict and control defects in catalyst-coated membranes. / text

Η παρούσα Μεταπτυχιακή εργασία πραγματεύεται την μεταφορά διατηρητικού ρύπου, ο οποίος εκρέει από γραμμική πηγή σταθερού μήκους, συνεχούς αλλά και στιγμιαίας έγχυσης, σε διαφορετικά βάθη ενός ανοικτού αγωγού με επίπεδο και υπό κλίση πυθμένα. Η επίλυση του προβλήματος της μεταφοράς ρύπου έγινε με τον εμπορικό κώδικα ANSYS FLUENT v.13 και στη συνέχεια συγκρίθηκε με τα αποτελέσματα που προκύπτουν από την αναλυτική λύση. / This master thesis is dealing with the mass transport problem of a conservative neutral pollutant inside an open channel flow. The open channel is flat bottommed with a mild slope. The pollutant outflows either continuously or instantaneously out of a linear source,with specified length, which every time is positioned on different depths. The mass transport problem was solved both numerically, by ANSYS FLUENT v.13 programme, and analytically in order to get those two types of solytions compared.

This thesis examined the effect of sub-boiling temperatures on subsurface flow and mass transport, as a result of electrical resistance heating (ERH). Low temperature ERH was simulated using a newly developed two-dimensional, electro-thermal, flow and transport model (ETM). To capture the non-isothermal processes in the subsurface during low temperature ERH, the ETM included temperature dependent equations for density, viscosity, and electrical conductivity. The model was validated with laboratory experiments in which voltage distribution, instantaneous power, temperature, and tracer transport were measured. Both the tracer experiments and the simulation results indicated that flow and contaminant movement could be significantly impacted by low temperature ERH due to temperature induced buoyant flow. In the first part of the thesis, the ETM was used to study the onset of buoyant flow in the subsurface and its effect on contaminant transport. Buoyant flow was predicted to occur when the ratio between the Rayleigh and thermal Peclet numbers (buoyancy ratio), was greater than 1. The buoyancy ratio was expressed in terms of subsurface temperature, thermal expansion coefficient and hydraulic gradient, thus facilitating its application to subsurface thermal activities. The effect of buoyant flow on contaminant transport was found to be dependent on the buoyancy ratio and Rayleigh number. The second part of the thesis examined the effect of soil heterogeneity, electrical conductivity and applied groundwater flux on energy and mass transport. To examine soil heterogeneity effects, random permeability fields for two aquifers with varying levels of heterogeneity were generated. Higher soil electrical conductivity values increased the power dissipated and resulted in shorter heating times and quicker onset of buoyant flow. Consequently, electrical conductivity had a statistically significant effect on the subsurface energy distribution. The applied groundwater flux had a strong effect on heat and mass transport with lower velocities resulting in upward plume movement due to buoyancy effects. In addition, buoyant flow was observed to dominate over flow through high permeability zones. The last chapter of the thesis investigated the formation and movement of discrete gas bubbles during ERH by combining ETM with a macroscopic invasion percolation (MIP) model. The model simulated soils with different permeabilities and entry pressures at various operating temperatures and groundwater velocities. It was observed that discrete bubble formation occurred in all soils, with upward mobility being limited by lower temperatures and higher entry pressures. By including the MIP model, the resulting aqueous concentrations were significantly different from results obtained with a conventional advective-dispersive model, especially in high permeability soils. This was due to bubbles moving to cooler areas, collapsing, and contaminating previously clean zones. The results of this thesis demonstrated that sub-boiling temperatures affect subsurface flow and mass transport, especially when temperature-induced buoyant flow occurred. Although this study focused on ERH applications, the results may be applicable to other subsurface thermal activities such as geothermal heating.

This thesis examined the effect of sub-boiling temperatures on subsurface flow and mass transport, as a result of electrical resistance heating (ERH). Low temperature ERH was simulated using a newly developed two-dimensional, electro-thermal, flow and transport model (ETM). To capture the non-isothermal processes in the subsurface during low temperature ERH, the ETM included temperature dependent equations for density, viscosity, and electrical conductivity. The model was validated with laboratory experiments in which voltage distribution, instantaneous power, temperature, and tracer transport were measured. Both the tracer experiments and the simulation results indicated that flow and contaminant movement could be significantly impacted by low temperature ERH due to temperature induced buoyant flow. In the first part of the thesis, the ETM was used to study the onset of buoyant flow in the subsurface and its effect on contaminant transport. Buoyant flow was predicted to occur when the ratio between the Rayleigh and thermal Peclet numbers (buoyancy ratio), was greater than 1. The buoyancy ratio was expressed in terms of subsurface temperature, thermal expansion coefficient and hydraulic gradient, thus facilitating its application to subsurface thermal activities. The effect of buoyant flow on contaminant transport was found to be dependent on the buoyancy ratio and Rayleigh number. The second part of the thesis examined the effect of soil heterogeneity, electrical conductivity and applied groundwater flux on energy and mass transport. To examine soil heterogeneity effects, random permeability fields for two aquifers with varying levels of heterogeneity were generated. Higher soil electrical conductivity values increased the power dissipated and resulted in shorter heating times and quicker onset of buoyant flow. Consequently, electrical conductivity had a statistically significant effect on the subsurface energy distribution. The applied groundwater flux had a strong effect on heat and mass transport with lower velocities resulting in upward plume movement due to buoyancy effects. In addition, buoyant flow was observed to dominate over flow through high permeability zones. The last chapter of the thesis investigated the formation and movement of discrete gas bubbles during ERH by combining ETM with a macroscopic invasion percolation (MIP) model. The model simulated soils with different permeabilities and entry pressures at various operating temperatures and groundwater velocities. It was observed that discrete bubble formation occurred in all soils, with upward mobility being limited by lower temperatures and higher entry pressures. By including the MIP model, the resulting aqueous concentrations were significantly different from results obtained with a conventional advective-dispersive model, especially in high permeability soils. This was due to bubbles moving to cooler areas, collapsing, and contaminating previously clean zones. The results of this thesis demonstrated that sub-boiling temperatures affect subsurface flow and mass transport, especially when temperature-induced buoyant flow occurred. Although this study focused on ERH applications, the results may be applicable to other subsurface thermal activities such as geothermal heating.

No description available.

Entwickelt wurde eine Konzeption zur Erstellung und Pilotanwendung eines gekoppelten Modellsystems für Sicker- und Grundwasser (ReArMo), das die prognostische Abschätzung künftiger Entwicklungen des Grundwassers nach Menge und Beschaffenheit unter geänderten Randbedingungen (Klima, Landnutzung, Bewirtschaftung) zum Ziel hat. Ein weiteres Ziel dieser Modellkopplung besteht in der Optimierung der Stickstoffdüngung bei relevanten landwirtschaftlichen Betrieben. Die zu betrachtenden Prozesse in der wechselfeuchten Bodenzone und im Grundwasser werden gemäß dem aktuellen Stand der Technik physikalisch fundiert erfasst.

In this thesis, a theoretical description of mass transport through membranes used in pervaporation separation processes has been investigated for both dense polymeric membranes and mixed matrix membranes (MMMs). Regarding the dense polymeric membranes, the Maxwell-Stefan model was extended to consider the effect of the operating temperature and membrane swelling on the mass transport of species within the membrane. The model was applied semi-empirically to predict the membrane properties and separation performance of a commercial Polydimethylsiloxane (PDMS) membrane used in the pervaporation separation of butanol from binary aqueous solutions. It was observed that the extended Maxwell-Stefan model has an average error of 10.5 % for the prediction of partial permeate fluxes of species compared to roughly 22% for the average prediction error of the Maxwell-Stefan model. Moreover, the parameters of the model were used to estimate the sorption properties and diffusion coefficients of components through the PDMS membrane at different butanol feed concentrations and operating temperatures. The estimated values of the sorption properties were observed to be in agreement with the literature experimental data for transport properties of butanol and water in silicone membranes while an exact comparison for the diffusion coefficient was not possible due to large fluctuations in literature values. With respect to the MMMs, a new model was developed by combining a one-directional transport Resistance-Based (RB) model with the Finite Difference (FD) method to derive an analytical model for the prediction of three-directional (3D) effective permeability of species within ideal mixed matrix membranes. The main novelty of the proposed model is to avoid the long convergence time of the FD method while the three-directional (3D) mass transport is still considered for the simulation. The model was validated using experimental pervaporation data for the separation of butanol from aqueous solutions using Polydimethylsiloxane (PDMS)/activated carbon nanoparticles membranes and using data from the literature for gas separation application with MMMs. Accurate predictions were obtained with high coefficient of regression (R2) between the calculated and experimental values for both applications.

Thesis advisor: Dunwei Wang / Electrochemical CO2 reduction reaction (CRR) provides a solution to both the increasing global demand of energy by forming valuable chemical products for fuel production, and global warming by reducing the amount of CO2 in the environment. To efficiently reduce CO2, we sought to understand the reaction mechanism using a polycrystalline Au electrode and the super concentrated LiTFSI solution (WiS) as the electrolyte. By varying both the electrolytic potential and the concentration of WiS, we investigated the factors determining product selectivity and found that reaction kinetics and mass transport together direct the selectivity towards CO. We probed the rate limiting step (RLS) of CO2 reduction by observing the variation of product distribution with water availability in solution, and discovered that the RLS was likely to involve only a single electron transfer to form COO*–. Lastly, we proposed that in WiS, H2O were the dominant proton sources for both CO2 reduction and H2 evolution reactions. In 21m WiS, the competing hydrogen evolution reaction was kinetically inhibited, so CO production was favored with a selectivity of 90% at a potential as early as -0.4V vs RHE. This study demonstrated the great potential of WiS as a platform for studying multi-proton, multi-electron transfer reactions. / Thesis (BS) — Boston College, 2018. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Scholar of the College. / Discipline: Chemistry.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22842号 / 工博第4782号 / 新制||工||1748(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 土居 伸二, 教授 木本 恒暢 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM