Within the European space programme, a new upper stage engine (Vinci) for the Ariane 5 launcher is being developed, and the Volvo Aero Corporation (VAC) is contributing with tur-bines for the fuel turbopumps. This MSc thesis investigates the possibility of designing the Turbine Exhaust Duct (TED) of the Vinci-engine in a carbon fibre composite material with adhesively attached titanium flanges. The focus of the project has been on stress analyses of the adhesive joints using Finite Element Methods (FEM), more specifically by using a cohe-sive zone material (CZM) to model the adhesive layer. Analysing adhesive joints is complex and an important part of the work has been to develop and concretise analysis methods for future use within VAC. To obtain the specialised material parameters needed for a CZM analysis, FE-models of ten-sile test specimens were analysed and the results compared to those of equivalent experimen-tal tensile tests. These parameters were then used when analysing the TED geometry with load cases specified to simulate the actual operation conditions of the Vinci engine. Both two-dimensional axisymmetric and fully three-dimensional models were analysed and, addition-ally, a study was performed to evaluate the effect of cryogenic temperatures on the strength of the joint. The results show that the applied thermal and structural loading causes local stress concentra-tions on the adhesive surface, but the stresses are not high enough to cause damage to the joint if a suitable joint design is used. Cryogenic temperatures (-150 °C) caused a significant strength reduction in the tensile specimens, partially through altered adhesive properties, but no such severe effects were seen in the temperature-dependent FE-analyses of the TED. It should be pointed out however, that some uncertainties about the material parameters exist, since these were obtained in a rather unconventional way. There are also several other impor-tant questions, beside the strength of the adhesive joint, that need to be answered before a metal-composite TED can be realised. / Volvo Aero deltar i utvecklingen av Vinci, en ny motor till det övre steget i den europeiska Ariane 5-raketen. Detta examensarbete behandlar möjligheten att tillverka ett turbinutlopp (TED) till vätgasturbinen i Vinci-motorn i kompositmaterial med flänsar i titan för att på så sätt uppnå en viktbesparing gentemot den tidigare konstruktionen i gjuten Inconel 718. Fokus har legat på att analysera hållfastheten i de limfogar som är tänkta att sammanfoga huvudröret med flänsarna, genom analyser med finita elementmetoden (FEM). Ett viktigt syfte har även varit att, för Volvo Aeros räkning, samla praktiska erfarenheter angående numerisk analys av limfogar, särskilt med användning av kohesiva zon-element för att modellera limfogen. FEM-analyser har gjorts av provstavsmodeller, där resultaten sedan jämförts med experimen-tella dragprovsresultat för att ta fram lämpliga material- och modelleringsparametrar för ana-lys med kohesiva zonelement. Därefter tillämpades dessa parametrar i analyser av den verkli-ga TED-geometrin med relevanta lastfall framtagna för att simulera driftsförhållandena i Vin-ci-motorn. Lastfallsanalyser med både tvådimensionellt axisymmetriska och tredimensionella geometrimodeller genomfördes, liksom uppskattningar av limfogens styrka vid kryogena driftstemperaturer. Resultaten pekar entydigt mot att en limfog med en ändamålsenlig tvärsnittsgeometri skulle hålla för de angivna lasterna utan att ta skada. De spänningskoncentrationer som uppstår ger lokalt höga spänningar i limmet, men inte på nivåer som skulle kunna orsaka brott. Det finns dock en viss osäkerhet angående riktigheten i materialparametrarna då en något okonventio-nell metod användes för att ta fram dessa. Flera stora frågor finns fortfarande kvar att besvara innan en metall-komposit konstruktion kan realiseras, inte minst hur flödeskammarens kom-plicerade geometri skall kunna tillverkas i kompositmaterial.

Understanding the hydrology of the riparian zone in a catchment can be an important prerequisite for determining solute loads and concentrations in streams. The riparian zone is the transition zone between surrounding landscape and an open water stream. This study focuses on the spatial and temporal variations of shallow groundwater levels in a forested headwater catchment in the Bergslagen area of central Sweden. Three snapshot campaigns were conducted during dry, humid and wet conditions to map the spatial variability of the groundwater levels. Piezometers giving the total hydraulic head were placed in the riparian zone along a stream network consisting of three first order streams and one second order stream. To asses temporal variations five groundwater wells were installed with automatic loggers to record continuous data during the wet period. Historical streamflow records from a permanent field station were collected and related to the groundwater levels in order to assess the relationship between groundwater levels and streamflow. Additionally a landscape analysis using GIS methods was conducted in order to identify potential drivers of spatial variation of groundwater levels in the riparian zone. The results showed that the slope could partially explain the observed spatial variability of riparian groundwater levels. The results from the spatially distributed piezometers and the continuously monitored groundwater wells with loggers were contradicting. Where the piezometers showed increasing depth to the groundwater table with increasing slope the loggers indicated the opposite. However, because the piezometers outnumbered the loggers the piezometer results can be considered more representative of the spatial variation of groundwater levels. There could be no general result concluded on the catchment scale but when looking at specific subcatchments it could be found that the variations in the riparian groundwater levels could be better explained where the stream had a more distinct channel. This indicates the importance to evaluate not only slope but the profile curvature as well for groundwater predictions.

CAD objects are geometrical descriptions of physical scenes from the real world. Ray tracing is used to project the objects onto a pixel screen. A lit and a shadow zone are formed according to the direction of the incoming field (light) and the orientation of the pixel screen. The arc length along the surface of the object, from the shadow boundary to a point in the lit zone, is computed by means of numerical integration. The arclengths corresponding to two orthogonal directions that are aligned with the pixels on the pixel screen are computed and used for interpolation to obtain the arc length for all directions. A number of simulations for various CAD geometries are made using a ray-tracer implemented in FORTRAN 90.

Near-surface sediments play an important role in governing the movement of water and contaminants from the land surface through the vadose zone to groundwater. Generally, low permeability surficial soils restrict water flow through the vadose zone and form a natural protective barrier to migration of surface applied contaminants. These types of fine-grained soils commonly contain macropores, such as fractures, animal burrows, and root holes, that have been identified as preferential flow pathways in the subsurface. Accordingly, macropores have the potential to influence groundwater recharge rates and compromise the protective capacity of surficial soils, particularly where the overburden is thin and aquifers are close to the surface. Partially saturated flow and transport in these environments is inherently complex and not well understood. The objective of this thesis was to examine preferential flow processes and the associated movement of contaminants in macroporous, low permeability soils. This was accomplished by conducting numerical and field experiments to investigate and describe the dynamics of macropore flow during episodic infiltration through the vadose zone and evaluate the corresponding influence of macropores on vertical water flow and contaminant transport. Numerical simulations were conducted to identify the important physical factors controlling flow and transport behaviour in partially saturated, fractured soils. A three-dimensional discrete fracture model, HydroGeoSphere, was used to simulate infiltration into homogeneous soil blocks containing a single vertical rough-walled fracture. Relatively large rainfall events with return periods ranging from 5 to 100 years were used, since they are more likely to generate significant preferential flow. Initial results showed that flow system dynamics were considerably more sensitive to matrix properties, namely permeability and antecedent moisture content, than fracture properties. Capillary forces, combined with the larger water storage capacity in the soil matrix, resulted in significant fracture-matrix interaction which effectively limited preferential flow down the fracture. It is also believed that fracture-matrix interaction reduced the influence of fracture roughness and other related small-scale fracture properties. The results imply that aperture variability within individual fractures may be neglected when modeling water flow through unsaturated soils. Nevertheless, fracture flow was still an important process since the fracture carried the majority of the water flow and virtually all of the mass of a surface applied tracer to depth in the soil profile. Model runs designed to assess transport variability under a variety of different physical settings, including a wider range of soil types, were also completed. Vertical contaminant fluxes were examined at several depths in the soil profile. The results showed that the presence of macropores (in the form of fractures) was more important than matrix permeability in controlling the rate of contaminant migration through soils. The depth of contaminant migration was strongly dependent on the antecedent moisture content and the presence of vertically connected fractures. Soil moisture content played a pivotal role in determining the onset and extent of preferential flow, with initially wet soils much more prone to macropore flow and deep contaminant migration. Simulations showed that surface applied tracers were able to reach the base of 2 m thick fractured soil profiles under wetter soil conditions (i.e., shallow water table). Likewise, long-duration, low-intensity rainfall events that caused the soil to wet up more resulted in proportionately more contaminant flux at depth. Fractured soils were particularly susceptible to rapid colloid movement with particle travel times to depths of 2 m on the order of minutes. The main implication is that the vulnerability of shallow groundwater is related more to vertical macropore continuity and moisture conditions in the soil profile, rather than traditional factors such as soil thickness and permeability. Macropore flow and transport processes under field conditions were investigated using small-scale infiltration experiments at sites in Elora and Walkerton, Ontario. A series of equal-volume infiltration experiments were conducted at both sites using a tension infiltrometer (TI) to control the (negative) infiltration pressures and hence the potential for macropore flow. A simulated rainfall experiment was also conducted on a small plot at Walkerton for comparison with the TI tests. Brilliant Blue FCF dye and fluorescent microsphere tracers were applied in all tests as surrogates for dissolved and colloidal contaminant species, respectively. Upon completion of infiltration, excavations were completed to examine and photograph the dye-stained flow patterns, map soil and macropore features, and collect soil samples for analysis of microspheres. Cylindrical macropores, in the form of earthworm burrows, were the most prevalent macropore type at both sites. In the TI tests, there was a clear relationship between the vertical extent of infiltration and the maximum pressure head applied to the TI disc. Larger infiltration pressures resulted in increased infiltration rates, more spatial and temporal variability in soil water content, and increased depths of dye penetration, all of which were attributed to preferential flow along macropores. Preferential flow was limited to tests with applied pressure heads greater than -3 cm. Under the largest applied pressures (greater than -1.0 cm), dye staining was observed between 0.7 and 1.0 m depth, which is near the seasonal maximum water table depth at both field sites. The tension infiltrometer was also used to infiltrate dye along an exposed vertical soil face, thereby providing a rare opportunity to directly observe transient macropore flow processes. The resulting vertical flow velocities within the macropores were on the order of tens of meters per day, illustrating the potential for rapid subsurface flow in macropores, even under partially saturated conditions. The results suggest that significant flow occurred in partially saturated macropores and this was supported by simple calculations using recent liquid configuration models for describing flow in idealized macropores. On all excavated sections, microspheres were preferentially retained (relative to the dye) in the top five centimeters of the soil profile. Below this zone, dye patterns correlated well with the presence of microspheres in the soil samples. There was evidence for increased retention of microspheres at lower water contents as well as a slightly greater extent of transport for smaller microspheres. In general, the microsphere and dye distributions were clearly dictated by vadose zone flow processes. As in the numerical experiments, water storage in the soil matrix and related macropore-matrix interaction were important factors. Mass transfer of water through the macropore walls promoted flow initiation in the macropores near surface. Deeper in the soil, water drawn away from the macropores into the matrix significantly retarded the downward movement of water along the macropores. Imbibition of dye from the macropores into the matrix was repeatedly observed on excavated soil sections and during the transient dye test. Microspheres were also transported laterally into the soil matrix indicating that conceptual models for colloid transport in the vadose zone need to account for this mass transfer process. Overall, the tension infiltrometer performed extremely well as a tool for controlling macropore flow under field conditions and, together with the dye and microsphere tracers, provided unique and valuable insights into small-scale flow and transport behavior. The field experiments raise concerns about the vulnerability of shallow groundwater in regions with thin, macroporous soils. Only a fraction of the visible macropores contributed to flow and transport at depths greater than 40 cm. However, with dye and microsphere transport observed to more than 1.0 m depth, rapid macropore flow velocities, and the sheer number of macropores present, there was clearly potential for significant flow and transport to depth via macropores. Under the right conditions, it is reasonable to speculate that macropores may represent a significant pathway for migration of surface applied contaminants to groundwater over the course of a single rainfall event.

Riparian zones (RZ) are known to act as buffers, reducing the transfer of potentially harmful nutrients from agricultural fields to surface water bodies. However, many of the same processes in the subsurface that help to reduce this nutrient loading, may also be leading to greenhouse gas (GHG) production and emissions from these areas. Agricultural riparian zones in Southern Ontario are often characterized by a sloped topography, with the highest topographic position being closest to the field edge, decreasing towards an adjacent stream or other surface water body. This topographic variability, combined with lateral chemical inputs from both upland areas and the stream, is expected to cause variable hydrochemical environments throughout the RZ, which may therefore lead to variable N2O dynamics between upland, mid-riparian and lowland areas. The objectives of this study were to examine these spatial trends in N2O production and resulting emissions, as related to the hydrochemical environment in these three distinct zones. Objectives were achieved by instrumenting 6 sites across two transects running perpendicular from the agricultural field edge, towards the stream edge, analyzing for subsurface N2O, moisture and temperature, groundwater NO3, NH4, dissolved organic carbon (DOC), dissolved oxygen, and surface fluxes of N2O. Subsurface N2O concentrations and ground water nutrient concentrations displayed distinct spatial and temporal/seasonal trends in the three positions across the RZ, however N2O fluxes across the soil-atmosphere interface did not display strong or consistent spatial trends. There was a disconnect between the subsurface variables and the fluxes at the surface, in that N2O emissions did not reflect the N2O concentrations produced in the shallow soil profile (150 cm deep), nor were they significantly related to the geochemical environment at each position. The lack of visible spatial trends in N2O fluxes may have been due to an “oxic blanket” effect which may divide the surface from the subsurface soil profile. As N2O fluxes in this study (-0.28 to 1.3 nmol m-2 s-1) were within the range observed at other, similar study sites, the oxic blanket doesn’t appear to impede concentrations of N2O reaching the soil-atmosphere interface. This may suggest that the N2O released as a flux was being produced in the very shallow soil profile (0 – 5 cm), above the soil gas profile arrays installed at this site. Subsurface concentrations of N2O were fairly high at certain depths and times, which was not reflected in the fluxes. This may have resulted from nitrifier denitrification reducing N2O to N2 before it reached the surface, in aerobic zones above the water table. Another potential reason for the lack of connection between subsurface processes and surface emissions was the high heterogeneity observed across the RZ, which may have overshadowed potential differences between positions. Physical soil properties like porosity and bulk density across the RZ also potentially impacted the N2O movement through the soil profile, resulting in similar fluxes among positions, and over time. The missing connection between subsurface N2O concentrations, ground water nutrients, and the surface fluxes was not a hypothesized result, and requires further research and analysis for a better understanding of the production and consequent movement of N2O.

This study extends the methodology for the delineation of capture zones to base flow contribution areas for stream reaches under the assumption of constant average annual base flow in the stream. The methodology is applied to the Alder Creek watershed in southwestern Ontario, using three different numerical models. The three numerical models chosen for this research were Visual Modflow, Watflow and HydroGeoSphere. Capture zones were delineated for three different stream segments with reverse particle tracking and reverse transport. The modelling results showed that capture zones delineated for streams are sensitive to the discretization scheme and the different processes considered (i.e. unsaturated zone, surface flow). It is impossible to predict the size, shape and direction of the capture zones delineated based on the model selected. Also, capture zones for different stream segments will reach steady-state at different times. In addition, capture zones are highly sensitive to differences in hydraulic conductivity due to calibration. It was found that finite element based integrated groundwater - surface water models such as HydroGeoSphere are advantageous for the delineation of capture zones for streams. Capture zones created for streams are subject to greater uncertainty than capture zones created for extraction wells. This is because the hydraulic gradients for natural features are very small compared to those for wells. Therefore, numerical and calibration errors can be the same order of magnitude as the gradients that are being modelled. Because of this greater uncertainty, it is recommended that particle tracking and reverse transport always be used together when delineating capture zones for stream reaches. It is uncertain which probability contour to choose when the capture zone is delineated by reverse transport alone. The reverse particle tracks help choose the appropriate probability contour to represent the stream capture zone.

A study of impulsively started flow over cylindrical objects is made using the particle image velocimetry (PIV) technique for Reynolds numbers of Re = 200, 500 and 1000 in an X-Y towing tank. The cylindrical objects studied were a circular cylinder of diameter, D = 25.4 mm, and square and diamond cylinders each with side length, D = 25.4 mm. The aspect ratio, AR (= L/D) of the cylinders was 28 and therefore they were considered infinite. The development of the recirculation zone up to a dimensionless time of t* = 4 following the start of the motion was examined. The impulsive start was approximated using a dimensionless acceleration parameter, a*, and in this research, the experiments were conducted for five acceleration parameters, a* = 0.5, 1, 3, 5 and 10. The study showed that conditions similar to impulsively started motion were attained once a* ¡Ý 3.<p> A recirculation zone was formed immediately after the start of motion as a result of flow separation at the surface of the cylinder. It contained a pair of primary eddies, which in the initial stages (like in this case) were symmetrical and rotating in opposite directions. The recirculation zone was quantified by looking at the length of the zone, LR, the vortex development, both in terms of the streamwise location and the cross-stream spacing of the vortex centers, a and b, respectively, as well as the circulation (strength) of the primary vortices, ¦£.<p> For all types of cylinders examined, the length of the recirculation zone, the streamwise location of the primary eddies and the circulation of the primary eddies increase as time advances from the start of the impulsive motion. They also increase with an increase in the acceleration parameter, a*, until a* = 3, beyond which there is no more change, since the conditions similar to impulsively started conditions have been achieved. The cross-stream spacing of the primary vortices is relatively independent of Re, a* and t* but was different for different cylinders.<p> Irrespective of the type of cylinder, the growth of the recirculation zone at Re = 500 and 1000 is smaller than at Re = 200. The recirculation zone of a diamond cylinder is much larger than for both square and circular cylinders. The square and diamond cylinders have sharp edges which act as fixed separation points. Therefore, the cross-stream spacing of the primary vortex centers are independent of Re, unlike the circular cylinder which shows some slight variation with changes in Reynolds number.<p> The growth of the recirculation is more dependent on the distance moved following the start of the impulsive motion; that is why for all types of cylinders, the LR/D, a/D and ¦£/UD profiles collapse onto common curves when plotted against the distance moved from the start of the motion.

The purpose of this study is to analyze and evaluate the suitability of the three instruments SERVQUAL, SERVPERF and Zone of tolerance to measure service quality, from the respondents' perspective. This study has been carried out by a quantitative method in which respondents answered three questionnaires, which was based on the three instruments. The SERVQUAL instrument is a revised version based on criticism by Carman (1990). It is based on the five dimensions; reliability, responsiveness, assurance, empathy and tangibility, with 22 items in which each dimension is associated with a number of items. SERVPERF is the instrument most similar to SERVQUAL and is also composed of the same five dimensions. The Zone of tolerance instrument is based on a three-column format of SERVQUAL, where each items is answered in the form of respondent's minimum service level, desired service level, and the perception of SL's service performance. The Zone of tolerance questionnaire consists of eight dimensions, including three new ones (convenience, connection, comfort) and 38 items. The theoretical frame of reference that includes Grönroos model of service quality, and the three instruments form the basis of the results, analysis and conclusion. In this study, we concluded that Zone of tolerance is the most suitable instrument for measuring the quality of service in public transport according to the respondents, thus it best describes the feelings that the respondents feel about the service quality of SL. There was however no significant difference between the Zone of tolerance and the SERVPERF instrument in this regard. The Zone of tolerance instrument was the most specific of the three, but we found that the instrument may undergo additional changes to make it more suitably. Although most respondents felt that the Zone of tolerance instrument was the best descriptive of how the respondents felt regarding the service quality of SL, a large proportion of respondents (49 %) found this instrument as the one that worst describe the feelings they felt regarding the service quality of SL. A large proportion (72 %) of respondents believe that the Zone of tolerance instrument is the most difficult to understand. This may be because it includes many items and that every item must answer three times, a rather unusual format. The fact that this instrument was the last one in the scheme may have a negative effect. Since respondents in the assessment of the last instrument certainly became bored and therefore may have led to the instrument not receiving as much attention as the two previous instruments.

<p>An advanced bulk constitutive model is used with a new cohesive zone model that is stress state and rate-dependent in order to simulate the ductile to brittle failure transition in polycarbonate. The cohesive zone model is motivated by experimental evidence that two different critical energies per unit area of crack growth exist in glassy polymers. A higher energy state is associated with ductile failure (slow crack growth), while a lower energy state is associated with brittle failure (fast crack growth). The model is formulated so that as rate or stress state changes within a simulation, the fracture energy and thus fracture mode may also change appropriately. The ductile to brittle transition occurs when the cohesive opening rate is over a threshold opening rate and when the stress state is close to plane strain in a fracture specimen. These effects are coupled. The principal contribution of this work is that this is the first time a single set of material input parameters can predict the transition from slow to fast crack growth as test loading rate and sample thickness are varied. This result enlisted the use of an advanced constitutive model and the new cohesive zone model with rate and stress-state dependencies in three-dimensional finite element analysis.</p> / Dissertation

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