A three dimensional numerical model for a micro proton exchange membrane fuel cell was developed to simulate the concentration distribution of the fuel gas, and analyze the flow field and current field in the fuel cell. Finite control volume scheme with SIMPLEC algorithm was employed in the numerical method. Various operating conditions on the performance of the fuel cell were studied. It was shown that the concentration of oxygen at the cathode can strongly influence the cell performance. Increase the operating temperature and the pressure of the inlet gas can improve the performance of the fuel cell.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis work aims to make a better knowledge on the insights of physics on microbubble coalescence process, using experimental and numerical approaches. The neck growth and bubble surface wave propagation at the early stage of coalescence, merging preference, as well as a reaction-channel modified microfluidic gas generator are presented in the thesis. Coalescence of unequal-sized microbubbles captive on solid substrate was observed from cross-section view using synchrotron high speed imaging technique and a mi- crofluidic gas generation device. The bridging neck growth and surface wave propaga- tion at the early stage of coalescence were investigated by experimental and numerical methods. The results show that theoretical half power law of neck growth rate is still valid when viscous effect is neglected. However, the inertial-capillary time scale is based on the radius of smaller parent microbubble. The surface wave propagation rate is proportional to the inertial-capillary time scale, which is based on the radius of larger parent microbubble of a coalescence pair. Meanwhile, the relationship of preference distance and size inequality microbub- bles were studied using the same micrfluidic gas generator and observation facilities. The size inequality of parent microbubbles would affect the preference distance of merged bubble in between. The merged bubble gets less closer to the larger parent bubble with an exponent of 1.82 as a reference, which largely affected by shear stress begotten on the solid interface. To express this phenomenon distinguished with free merging bubble pair, we propose the wall shear stress hinders the process of that parent bubbles move towards to each other during coalescence Our hypothesis was confirmed by identical coalescence simulation via ANSYS Fluent. To address the multiple measurement, utilization of Java based photography pro- cessing software ImageJ was applied as a key point to the thesis work. To acquire more microbubble coalescence cases on experiment for study, we enhanced the perfor- mance of microfluidic gas generator with reaction channel optimization. An optimized design on increasing the number of parallel reaction channel from single to triple, was applied to obtain a higher gas generation rate. Also the gas vent shape was modified from triangle to rectangle to provide more information on reaction channel optimiza- tion. The gas generation rate and H2O2 conversion rate were provided to further discuss.

Polymeric materials have attracted a lot of attention for the past several decades. Different sectors of manufacturing industry, such as packaging, building and automotive industry have introduced polymeric materials in their applications. Common polymer manufacturing processes include thermoforming and blow molding. In this research, characteristics of a new polymer manufacturing process, referred to as axial-feed hot gas tube forming (HGTF) are studied. Experimental studies were conducted to form a simple axisymmetric component from extruded polypropylene (PP) tube by varying several key process parameters such as internal pressure, temperature and axial feed. Tube shape and deformation characteristics were studied as a function of the above process parameters. In addition, two consecutive material models have been utilized for finite element simulation of axial-feed HGTF of PP tube using a commercial FE code. One of them is conventional hyperelastic Ogden material model and another is more advanced viscoelastic-viscoplastic Augmented Hybrid material model (AHM), that has been recently developed. Simulation results from two models were analyzed and compared with the experimental results and good general agreement has been obtained. Results showed that application of more advanced AHM material model led to improved prediction of part shape and strain distribution over the part profile. / Thesis / Master of Applied Science (MASc)

Frozen soil has a major effect in many hydrologic processes, and its impacts are difficult to predict. A prime example is flood forecasting during spring snowmelt within the Canadian Prairies. One key driver for the extent of flooding is the antecedent soil moisture and the possibility for water to infiltrate into (partly) frozen soils. Therefore, these situations are crucial for accurate flood prediction at every spring. The main objective of this study was to evaluate the water flow and heat transport within available hydrological models to predict the impact of frozen and partly frozen soil on infiltration and percolation. A standardized data set was developed for water flow and heat transport into (partial) frozen soil by laboratory experiments using fine sand within a one-dimensional (1-D) soil column. A 1-D soil column having a length of 107 cm and diameter of 35.6 cm was built and equipped with insulation to limit heat exchange only through the soil surface. A data logger collected the moisture content and temperature by five FDR sensors which have been installed at a distance of 15 cm from each other. During the experiments, temperature, soil moisture, and percolated water was observed at different freezing conditions (-5°C, -10°C, and -15°C) as well as at thawing conditions when the air temperature was increased to +5°C. Distribution of soil moisture and soil temperature in the soil column was plotted for the experimental data over the freezing and thawing period. As some of the water in the soil begins to freeze, a decrease in water content was observed with a sudden increase in soil temperature near 0°C or slightly below of 0°C. This was, in fact, only a decrease in unfrozen water, not a decrease in total water content and was caused by the latent heat during freezing. Soil temperature showed noticeable differences at the top and the bottom of soil column during the change of state of water. The heat flux at the lower soil column was strongly limited due to iii the overlying soil. Thus, the soil temperature at the lowest sensors stayed in a freezing condition over several days and was not changing the temperature due to the latent heat which was released during the freezing process. Significant variation in soil moisture content was found between the top and the bottom of the soil column at the starting of the thawing period. However, with increasing temperature, the lower depth of the soil column showed higher moisture content as the soil was enriched with moisture with higher transmission rate due to the release of heat by soil particles during the thawing cycle. The soil system did not remain in the isothermal state during the thawing cycle. Although gravitational gradient was mainly responsible for the infiltration rate into the partially frozen soil, the distribution of moisture was greatly influenced by the temperature gradient. Vadose zone modeling using HYDRUS-1D was applied to the data set. Numerical results of the modeling were calibrated using the experimental results. It showed that the newly developed benchmark data set were useful for the validation of numerical models. The use of such a validated freezing and thawing module implemented into larger scale hydrologic models will directly reduce the prediction uncertainty during flood forecasting. Moreover, these benchmark data sets will be useful for the validation of numerical models and for developing scientific knowledge to suggest potential code variations or new code development in numerical models. / February 2017

Since the devastating hurricane seasons of 2004, 2005, and 2008, the stability and serviceability of coastal bridges during and following hurricane events have become a main public concern. Twenty coastal bridges, critical for hurricane evacuation and recovery efforts, in Texas have been identified as vulnerable to hurricane surge and wave action. To accurately assess extreme surges at these bridges, a dimensionless surge response function methodology was adopted. The surge response function defines maximum surge in terms of hurricane meteorological parameters such as hurricane size, intensity, and landfall location. The advantage of this approach is that, given a limited set of discrete hurricane surge data (either observed or simulated), all possible hurricane surges within the meteorological parameter space may be described. In this thesis, we will first present development of the surge response function methodology optimized to include the influence of regional continental shelf geometry. We will then demonstrate surge response function skill for surge prediction by comparing results with surge observations for Hurricanes Carla (1961) and Ike (2008) at several stations along the coast. Finally, we apply the improved surge response function methodology to quantify extreme surges for Texas coastal bridge probability and vulnerability assessment.

Computational fluid dynamics (CFD) has been extensively used in the study of building energy usage and thermal comfort in buildings, however there remains the need to thoroughly evaluate the accuracy of the results given by such CFD methods. The present study involves a numerical investigation of the flow and temperature distribution in the atrium situated in the Concordia University Engineering Building. The study involved a steady-state simulation of the conditions in the atria on August 1, 2007, a date for which experimental data was available for validation of the numerical results. The commercial CFD solver FLUENT was used to solve the equations that govern the flow in the atrium. The realizable k- turbulence model incorporating buoyancy force effects was used. During the period studied a forced airflow through the atrium existed due to a mechanical air supply vent near the floor level. The natural convection in the atrium, induced by the temperature differences resulting mainly from the incoming solar radiation, was modeled using the bousinessq approximation. In general, good agreement was obtained between the numerical and experimental results. The numerical results also predicted the thermal stratification in the atrium relatively accurately. A parametric study was performed to assess the sensitivity of the numerical results to the assumed boundary conditions used in the study. An evaluation of the thermal comfort levels in the atrium was also undertaken using the numerical results. This indicated that while regions of thermal discomfort did exist in the atrium, these regions constituted only a small part of the atrium. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-09-25 17:29:46.857

Afin de faciliter le séquençage des génomes, une troisième génération de systèmes de séquençage est nécessaire. La translocation de biomolécules est le phénomène clé mis en jeu dans l'optique d'un séquençage par nanopore. Nous nous sommes intéressé à ce phénomène avec une approche à la fois théorique et numérique. Dans le cadre de nos travaux, nous avons tout d'abord élaboré un modèle dit gros grain de polymère structuré (présentant une structure proche de celle de l'ADN) adapté à une étude par dynamique moléculaire. Après avoir vérifié la pertinence de notre modèle avec les lois de la physique statistique des polymères, nous nous sommes concentrés sur la translocation. Nous avons revisité le cas standard d'un nanopore au sein d'une membrane fixe et proposé un modèle théorique dans le cas de la traction du polymère. L'arrivée des membranes fines, clés du succès d'un éventuel séquençage non destructif par nanopore entraine de nouvelles intéractions avec la membrane qui n'ont pas encore été étudiées. Nous présentons la première étude numérique de grande ampleur sur ses intéractions. Nos résultats permettent d'étudier l'influence des vibrations, de la déformabilité et de la flexibilité de la membrane. / So as to facilitate genomic sequencing, a third generation of sequencing devices is needed. Biopolymer translocation is the key phenomenon involved in nanopore sequencing prospects. We investigated this phenomenon through both theoretical and numerical approaches. Our work started with devicing a coarse grained structured polymer (with a DNA like structure) adapted to a molecular dynamics study. Once we have verified the reliability of our model towards statistical polymer physics, we focused on translocation. We reinvestigated the common case of a nanopore within a fix membrane and proposed a theoretical model for translocation under a pulling force. The arrival of thin membranes is key to an eventual success of non destructive sequencing with a nanopore. This enables new interactions with the membrane which have not been investigated yet. We provide the first large scale numerical investigation of such interactions. our results provide an insight over the influence of membrane vibrations, deformability and flexibility.

Numerical calculations were performed over a variety of two-dimensional rib roughness configurations in which the ratio of flow depth to roughness height was varied from 1.1 to 40. Periodically fully developed flow was achieved by employing periodic boundary conditions and the effect of turbulence was accounted for by a two-layer model. These calculations were used to test the hypothesis that any rough wall resistance may be reduced to an equivalent wall shear stress located on a plane wall. The position of the plane wall is determined by a novel method of prediction obtained by consideration of strearnwise force moments. The resistance is then determined by three dynamically significant length scales: the first (yo) specifies the position of the equivalent plane wall, the second is the depth of flow h and the third is similar to Nikuradse's sand grain roughness k,,. The latter length scale is however depth dependent and a universal relationship is postulated: ks y,, -,= F/Tk where ksw is the asymptotic value of ks at very large flow depths. For the calculation of friction factor, a resistance equation is proposed of the form typical of fully rough flows. These postulates are supported by the numerical model results though further work including physical experiments is required to confirm them. Before applying the two-layer model to this problem it was tested on smooth rectangular duct flows and Schlichting's (1936) long angle roughness experiments. The opportunity was taken to further explore these flows, and in addition calculations were carried out for Grass et al's (1991) open channel rib roughness experiments. The periodic boundary conditions were also applied to a larninar counter-flow plate-fin heat exchanger. A novel source-sink arrangement for heat flux was developed in order to implement these boundary conditions.

Numerical calculations were performed over a variety of two-dimensional rib roughness configurations in which the ratio of flow depth to roughness height was varied from 1.1 to 40. Periodically fully developed flow was achieved by employing periodic boundary conditions and the effect of turbulence was accounted for by a two-layer model. These calculations were used to test the hypothesis that any rough wall resistance may be reduced to an equivalent wall shear stress located on a plane wall. The position of the plane wall is determined by a novel method of prediction obtained by consideration of strearnwise force moments. The resistance is then determined by three dynamically significant length scales: the first (yo) specifies the position of the equivalent plane wall, the second is the depth of flow h and the third is similar to Nikuradse's sand grain roughness k,,. The latter length scale is however depth dependent and a universal relationship is postulated: ks y,, -,= F(Tkwhere ksw is the asymptotic value of ks at very large flow depths. For the calculation of friction factor, a resistance equation is proposed of the form typical of fully rough flows. These postulates are supported by the numerical model results though further work including physical experiments is required to confirm them. Before applying the two-layer model to this problem it was tested on smooth rectangular duct flows and Schlichting's (1936) long angle roughness experiments. The opportunity was taken to further explore these flows, and in addition calculations were carried out for Grass et al's ( 199 1) open channel rib roughness experiments. The periodic boundary conditions were also applied to a larninar counter-flow plate-fin heat exchanger.A novel source-sinka rrangemenfto r heat flux was developedi n order to implement these boundary conditions.

Treated and untreated liquid that is discharged from industrial and desalination plants is one of the main factors that break the ecological balance and destroys aquatic habitat in lakes, rivers and coastal areas where the effluent is discharged. Positively and negatively buoyant jets are two categories of outfalls which are generated because of the destiny difference between the effluent and ambient fluid. In order to ensure minimal impact of the effluent on the environment, it is necessary to estimate the dilution of the jet and compare it with environmental regulations on the level of required dilution to ensure that the concentration of the effluent is diluted quickly enough and the concentration of the effluent at different points does not exceed the allowed concentrations. This study investigated the positively buoyant jet, which happens near the coastal and near water area. For instance, cooling water that flows out from a power plant or factory, wasted water that is discharged from an industrial plant near river, submerged drainage from civil municipal sewer systems and treated water from desalination plant in coastal area. Density difference, velocity and inclined angle of the jet were considered as the main factors that contribute to the jet spreading and were compared to develop the best solution for its dilution. The jet was discharged inclined downward to allow for more mixing and dilution of the effluent with the ambient water. In order to simulate a positive jet, tap water was injected in saline ambient. A large number of experiments were conducted in the laboratory and using camera imaging. The jet trajectory was estimated from the images using image processing and the impact of various parameters such as Froude number and jet velocity were investigated. The opensource software OpenFOAM, was employed for numerical simulations which is a finite volume model ensures mass conservation and allows for flexible mesh size for further accuracy and optimization of computational cost. Using this Computational Fluid Dynamics (CFD) model, the numerical simulations were performed, and the results were compared with laboratory experiments. A Reynold-Averaged Navier-Stokes (RANS) approach was employed in the numerical simulations which offers a good balance between accuracy and computational cost. It was found that the numerical model in conjunction with the second order turbulence model called Launder-Reece- Rodi model (LRR) had a reasonable agreement with the experimental data.