During the development of flight tests of a spacecraft, heat exchange occurs among the many physically separated subsystem surfaces through the phenomenon of thermal radiation. Considering the increasing complexity of the geometrical forms and shapes in the design of such systems, the monitoring and control of the radiative heat fluxes taking place in the multi-reflecting, absorbing and emitting heat transfer environment are very critical. Because the analytical solution of thermal radiation in such geometrically complex three-dimensional systems is not practical, extensive numerical modelling techniques are widely used to predict radiative heat fluxes on the many thermally active surfaces. From experience, it is found that this can be very difficult and not at all commensurate with fast feedback unless the analysis is from a simple system layout. Considering that a relatively new approach dedicated to the basic analysis of radiative heat flux has been developed by the heat transfer community as a numerical approximation called the Discrete Ordinates Method (DOM), a first question did arise in terms of how well an enhanced and more comprehensive formulation based on this concept would fulfil the task of achieving faster results whilst still accurately predicting radiative heat transfer in three-dimensional, more complex geometries.

Conventional disposal of waste rock results in the construction of benches with interbedded fine and coarse layers dipping at the angle of repose. The waste rock benches are typically 20-meters in height and are constructed in a vertical sequence to form waste rock dumps commonly greater than 100-meters high. The interbedded structure influences the flow pathways for infiltration water within the waste rock profile. Preferential flow pathways develop when one material becomes more conductive than the surrounding material. The flow of meteoric waters through the interbedded waste rock structure is difficult to describe since the dumps are constructed above natural topography and are generally unsaturated. Two previous research studies were undertaken at the University of Saskatchewan to study end dumped waste rock piles and the relationship to preferential flow for unsaturated conditions. The first study was conducted during the excavation of a large waste rock pile at Golden Sunlight Mine in Montana (Herasymuik, 1996). Field observations showed that the waste rock pile consisted of steeply dipping fine and coarse-grained layers. The results of further laboratory analysis indicated the potential for preferential flow through the fine-grained material under conditions with negative pore-water pressures and unsaturated flow. The second study investigated the mechanism for preferential flow in vertically layered, unsaturated soil systems (Newman, 1999). The investigation included a vertical two-layer column study and a subsequent numerical modelling program showing that water prefers to flow in the finer-grained material. The preferential flow path was determined to be a function of the applied surface flux rates and the unsaturated hydraulic conductivity of the fine-grained material layer. A numerical modelling program to evaluate preferential flow was conducted for the present study in an inclined four-layer system consisting of alternating fine and coarse-grained waste rock. The numerical modelling program was undertaken using the commercial seepage software package, Seep/W, that is commonly used by geotechnical engineers. The result obtained using Seep/W showed preferential flow to occur in the fine-grained layer. However, difficulties with respect to convergence under low flow conditions with steep hydraulic conductivity functions were encountered. A comprehensive sensitivity analysis was completed to investigate the factors that influence convergence in the Seep/W model including: convergence criteria, mesh design and material properties. It was found that the hydraulic conductivity function used for the coarse-grained material was the most important factor. The problem of the steep slope for the hydraulic conductivity function specified for the coarse-grained material was solved by progressively decreasing the slope of the hydraulic conductivity function at 10-8 m/s (for applied fluxes of 10-7 m/s or less). The sensitivity analysis showed that the manipulation of the hydraulic conductivity function had insignificant changes in the flux distribution between the waste rock layers and great significance for achieving convergence. Based on the discoveries of the sensitivity analysis, a 20-meter high multi-layer waste rock profile inclined at 50º with an applied flux of 7.7e10-9 m/s equal to the annual precipitation at the Golden Sunlight Mine was successfully simulated. A parametric study was subsequently conducted for an applied flux rate of 10-5 m/s for slope heights of 1-meter to 20 meters with slope angles varying between 45º and 90º. The parametric study demonstrated that flow in a multi-layered waste rock dump is a function of inclination, contact length between the layers, and the coarse and fine-grained hydraulic properties for the waste rock. An alternative numerical modelling technique based on a modified Kisch solution was also used to investigate preferential flow. The Kisch method helped to verify and simplify the numerical problem as well as to illustrate the mechanics of preferential flow in a two-layered system. In general, commercial seepage modeling packages are powerful and useful tools that are designed to adequately accommodate a wide range of geotechnical problems. The results of this research study indicate that Seep/W may not be the best-suited tool to analyze unsaturated seepage through sloped waste rock layers. However, numerical modelling is a process and working through the process helps to enhance engineering judgment. The Seep/W model provided an adequate solution for a simplified simulation of unsaturated seepage through waste rock layers. The modified Kisch solution independently verified the solution and provided additional confidence for the results of Seep/W model.

Conventional disposal of waste rock results in the construction of benches with interbedded fine and coarse layers dipping at the angle of repose. The waste rock benches are typically 20-meters in height and are constructed in a vertical sequence to form waste rock dumps commonly greater than 100-meters high. The interbedded structure influences the flow pathways for infiltration water within the waste rock profile. Preferential flow pathways develop when one material becomes more conductive than the surrounding material. The flow of meteoric waters through the interbedded waste rock structure is difficult to describe since the dumps are constructed above natural topography and are generally unsaturated. Two previous research studies were undertaken at the University of Saskatchewan to study end dumped waste rock piles and the relationship to preferential flow for unsaturated conditions. The first study was conducted during the excavation of a large waste rock pile at Golden Sunlight Mine in Montana (Herasymuik, 1996). Field observations showed that the waste rock pile consisted of steeply dipping fine and coarse-grained layers. The results of further laboratory analysis indicated the potential for preferential flow through the fine-grained material under conditions with negative pore-water pressures and unsaturated flow. The second study investigated the mechanism for preferential flow in vertically layered, unsaturated soil systems (Newman, 1999). The investigation included a vertical two-layer column study and a subsequent numerical modelling program showing that water prefers to flow in the finer-grained material. The preferential flow path was determined to be a function of the applied surface flux rates and the unsaturated hydraulic conductivity of the fine-grained material layer. A numerical modelling program to evaluate preferential flow was conducted for the present study in an inclined four-layer system consisting of alternating fine and coarse-grained waste rock. The numerical modelling program was undertaken using the commercial seepage software package, Seep/W, that is commonly used by geotechnical engineers. The result obtained using Seep/W showed preferential flow to occur in the fine-grained layer. However, difficulties with respect to convergence under low flow conditions with steep hydraulic conductivity functions were encountered. A comprehensive sensitivity analysis was completed to investigate the factors that influence convergence in the Seep/W model including: convergence criteria, mesh design and material properties. It was found that the hydraulic conductivity function used for the coarse-grained material was the most important factor. The problem of the steep slope for the hydraulic conductivity function specified for the coarse-grained material was solved by progressively decreasing the slope of the hydraulic conductivity function at 10-8 m/s (for applied fluxes of 10-7 m/s or less). The sensitivity analysis showed that the manipulation of the hydraulic conductivity function had insignificant changes in the flux distribution between the waste rock layers and great significance for achieving convergence. Based on the discoveries of the sensitivity analysis, a 20-meter high multi-layer waste rock profile inclined at 50º with an applied flux of 7.7e10-9 m/s equal to the annual precipitation at the Golden Sunlight Mine was successfully simulated. A parametric study was subsequently conducted for an applied flux rate of 10-5 m/s for slope heights of 1-meter to 20 meters with slope angles varying between 45º and 90º. The parametric study demonstrated that flow in a multi-layered waste rock dump is a function of inclination, contact length between the layers, and the coarse and fine-grained hydraulic properties for the waste rock. An alternative numerical modelling technique based on a modified Kisch solution was also used to investigate preferential flow. The Kisch method helped to verify and simplify the numerical problem as well as to illustrate the mechanics of preferential flow in a two-layered system. In general, commercial seepage modeling packages are powerful and useful tools that are designed to adequately accommodate a wide range of geotechnical problems. The results of this research study indicate that Seep/W may not be the best-suited tool to analyze unsaturated seepage through sloped waste rock layers. However, numerical modelling is a process and working through the process helps to enhance engineering judgment. The Seep/W model provided an adequate solution for a simplified simulation of unsaturated seepage through waste rock layers. The modified Kisch solution independently verified the solution and provided additional confidence for the results of Seep/W model.

Over one million simulations were conducted using the Hec-Ras4b (US Army Corps of Engineers, 2004) model to evaluate the sensitivity of model predictions to field data accuracy, density and estimation techniques and provide guidance towards balancing human resource allocation with model accuracy. Notable differences were identified in model accuracy if a project is concerned with river processes occurring within the limits of the bankfull channel versus floodplain regions. Increased cross section discretization, bankfull channel detail and main channel roughness were of greatest field survey and measurement importance when processes relevant to the bankfull channel are of concern (i.e. geomorphic processes or sediment transport). Conversely, where flood conditions are of highest consideration, estimates of floodplain roughness dominate the accuracy of the results of computed water surface elevations. Results for this case study also demonstrate that higher orders of total station field surveys provide little additional accuracy in final predicted water surface elevations, relative to proper estimates of in-channel and floodplain roughness. As long as drift in field surveys has been accounted for during or subsequent to total station surveys, survey techniques such as hangers can be readily employed with very little increase in final model prediction error, while improving field data acquisition efficiency.

Over one million simulations were conducted using the Hec-Ras4b (US Army Corps of Engineers, 2004) model to evaluate the sensitivity of model predictions to field data accuracy, density and estimation techniques and provide guidance towards balancing human resource allocation with model accuracy. Notable differences were identified in model accuracy if a project is concerned with river processes occurring within the limits of the bankfull channel versus floodplain regions. Increased cross section discretization, bankfull channel detail and main channel roughness were of greatest field survey and measurement importance when processes relevant to the bankfull channel are of concern (i.e. geomorphic processes or sediment transport). Conversely, where flood conditions are of highest consideration, estimates of floodplain roughness dominate the accuracy of the results of computed water surface elevations. Results for this case study also demonstrate that higher orders of total station field surveys provide little additional accuracy in final predicted water surface elevations, relative to proper estimates of in-channel and floodplain roughness. As long as drift in field surveys has been accounted for during or subsequent to total station surveys, survey techniques such as hangers can be readily employed with very little increase in final model prediction error, while improving field data acquisition efficiency.

CRISSP2D, a two-dimensional finite element model, was used to undertake a comprehensive hydrodynamic, thermodynamic, and dynamic ice study on the Red River near Netley Cut in order to determine the cut's effect on the local hydrodynamics and freeze-up processes. Open water hydrodynamic and thermodynamic models were developed, calibrated, and verified such that the measured data and simulation results were in acceptable agreement. These models were used as input to the dynamic ice model which was able to adequately predict ice thickness within the study area once the air-ice heat transfer coefficient was calibrated. The geometry of the dynamic ice model was subsequently altered to simulate the effects of sealing Netley Cut. The geometry change resulted in no noticeable difference in simulated ice thickness, but did affect the hydrodynamics within the study area. In particular, the water velocity in the Red River downstream of Netley Cut and water surface elevation upstream of Netley Cut both increased noticeably.

Wildland fires are a type of vegetation fire that burn in a rural or wild landscape and affect many countries worldwide. They are an important mechanism in ecosystem maintenance, although in certain cases wildland fires can adversely affect both people and the environment. A wildland fire can interact with the surrounding topography, vegetation and weather in a complex manner, which makes microscale prediction of wildland fire behaviour difficult in many situations. This thesis focused on the application of the Weather Research and Forecast (WRF) numerical weather prediction (NWP) and WRF-Fire coupled atmosphere-fire models to investigating aspects of atmospheric interactions with wildland fire. The research covered a wide range of atmospheric scales, from a seasonal mesoscale analysis of fire weather conditions across New Zealand to a microscale analysis of complex atmosphere-fire interactions over idealised terrain. The first study investigated the suitability of WRF modelling of fire weather conditions for the 2009/10 wildland fire season in New Zealand. The WRF model horizontal grid spacing was 8 km and the model output was directly compared with near-surface fire weather conditions meaured and derived at 23 weather stations located throughout New Zealand. The analysis considered the air temperature, relative humidity, wind conditions, rainfall and the New Zealand Fire Weather Index (FWI) and Continuous Haines Index (CHI) on observed high-end fire weather days. WRF typically underpredicted the air temperatures and relative humidities, whereas it typically overpredicted the wind speeds, CHI and the number of high-end fire weather days. WRF was assessed to be unsuitable for accurately modelling particular aspects of fire weather, such as the wind speed and direction, in mountainous terrain and near complex coastlines. Further research is needed to investigate how varying the horizontal resolution in WRF affects the assessed accuracy of modelled fire weather conditions. The second study investigated the behaviour of the Haines Index (HI), CHI and FWI, and their associated atmospheric properties for the 2009/10 wildland fire season in New Zealand. The analysis demonstrated that there was a large degree of spatial variability in fire weather conditions throughout New Zealand, particularly in or near mountainous terrain. The fire weather severity was highest in the eastern South Island and appeared to be closely associated with mesoscale atmospheric processes over mountainous terrain, although the relationship between these atmospheric processes and fire weather condi- tions requires further investigation. The HI and CHI were both limited in their utility at measuring aloft fire weather conditions in high altitude regions. Finally, the fire weather conditions associated with the 36 largest wildland fires of the fire season were evaluated, although no statistical relationships were found between the wildland fire size and either the CHI or FWI. The third study investigated the fire weather conditions across the South Island associated with an extreme foehn event on 6 February 2011. Mountain waves developed in the northwesterly synoptic flow over the Southern Alps and were found to directly influence the fire weather conditions near the surface and aloft in the lee of the mountains. A hydraulic jump along the foothills of the Canterbury Plains resulted in a downslope windstorm with wind speeds exceeding 80 km/h. Further south, large amplitude mountain lee waves directly influenced the near-surface wind speeds and atmospheric stability aloft. The foehn winds were associated with peak air temperatures over 35˚C in the eastern South Island, which are significantly higher than the climatological average. The FWI indicated widespread extreme near-surface fire weather conditions in the lee of the mountains. The subsequent passge of a cold front on 7 February brought a marked reduction in fire weather severity across the South Island. The fourth study investigated atypical wildland fire behaviour on steep leeward slopes through a series of idealised WRF-Fire simulations. The analysis considered both the leeward flow characteristics over a triangular ridge line and the fire spread from an ignition point at the base of the leeward slope. The fire spread was modelled for two different fuel types and with two-way atmosphere-fire coupling both enabled and disabled. The modelled fire spread in the heavy fuel type with coupling enabled closely resembled the fire channelling wildland fire behaviour phenomenon. The initial fire spread was initially dominated by upslope fire spread to the mountain ridge line at an average rate of around 2.0 km/h. This was followed by a phase of intermittent rapid lateral fire spread close to the ridge line at a maximum rate of around 3.6 km/h. The intermittent rapid lateral fire spread was driven by strongly circulating horizontal near-surface winds that were associated with updraft-downdraft interfaces. These updraft-downdraft interfaces formed due to an interaction between the strong pyro-convection and terrain-modified winds. The presented research collectively demonstrated the versatility and effectiveness of NWP and coupled atmosphere-fire modelling for studying various aspects of atmospheric interactions with wildland fire. The research further highlighted the effects of atmospheric processes over complex terrain on fire weather conditions and wildland fire behaviour. Although three of the studies in the thesis had a regional focus on New Zealand, the research outcomes should benefit end users in fire management worldwide.

Hydrothermal circulation through the seafloor on the mid-ocean ridge flanks is responsible for globally significant fluid, heat and chemical fluxes between the ocean and the oceanic crust. This dissertation investigates the locations of fluid ingress and egress, fluid flow paths within the crust, and the hydrology of the crust. Based on a global compilation of sediment interstitial water chemistry and models of interstitial water chemical transport and reaction, it is found that <10% of the ridge flank hydrothermal fluid flux passes through marine sediments globally. This requires that the large majority of hydrothermal fluid enters and leaves the crust through exposed basement outcropping through the sediment (“outcrops”). A probabilistic model of basement topography and sedimentation was used to quantify the distribution of seafloor outcrops globally, estimating that outcrops are, on average, a few kilometres apart on young crust, increasing to tens of kilometres apart as the crust ages. A model in which fluid travels laterally within the crustal aquifer for kilometres to tens of kilometres between discrete outcrops (“outcrop-to-outcrop flow”) is consistent with the global heat flow data. This finding supports the proposition that outcrop-to-outcrop flow is the dominant mode of ridge flank hydrothermal circulation globally. An alternative model of ridge flank hydrothermal circulation in which fluid circulation occurs by local convection within isolated outcrops is also possible, and is probably the dominant mode of circulation in crust younger than 3-5 Myrs old, on average, where there is insufficient sediment cover to support the lateral pressure gradients required by outcrop-to-outcrop flow. Estimated crystallization temperatures of carbonate minerals in the crust suggest that, at some locations in the aquifer, local convective mixing may be restricted (i.e., the aquifer is poorly mixed), whereas the carbonate data for other locations cannot distinguish between a well mixed and a poorly mixed aquifer. A poorly mixed aquifer requires that vertical permeability is 1.5 - 2.5 orders of magnitude lower than horizontal permeability. This permeability anisotropy may arise from interlaying of different lithological units within the upper crust. / Graduate / 0388 / 0547 / brocka@uvic.ca

CRISSP2D, a two-dimensional finite element model, was used to undertake a comprehensive hydrodynamic, thermodynamic, and dynamic ice study on the Red River near Netley Cut in order to determine the cut's effect on the local hydrodynamics and freeze-up processes. Open water hydrodynamic and thermodynamic models were developed, calibrated, and verified such that the measured data and simulation results were in acceptable agreement. These models were used as input to the dynamic ice model which was able to adequately predict ice thickness within the study area once the air-ice heat transfer coefficient was calibrated. The geometry of the dynamic ice model was subsequently altered to simulate the effects of sealing Netley Cut. The geometry change resulted in no noticeable difference in simulated ice thickness, but did affect the hydrodynamics within the study area. In particular, the water velocity in the Red River downstream of Netley Cut and water surface elevation upstream of Netley Cut both increased noticeably.

Hydrothermal circulation through the seafloor on the mid-ocean ridge flanks is responsible for globally significant fluid, heat and chemical fluxes between the ocean and the oceanic crust. This dissertation investigates the locations of fluid ingress and egress, fluid flow paths within the crust, and the hydrology of the crust. Based on a global compilation of sediment interstitial water chemistry and models of interstitial water chemical transport and reaction, it is found that <10% of the ridge flank hydrothermal fluid flux passes through marine sediments globally. This requires that the large majority of hydrothermal fluid enters and leaves the crust through exposed basement outcropping through the sediment (“outcrops”). A probabilistic model of basement topography and sedimentation was used to quantify the distribution of seafloor outcrops globally, estimating that outcrops are, on average, a few kilometres apart on young crust, increasing to tens of kilometres apart as the crust ages. A model in which fluid travels laterally within the crustal aquifer for kilometres to tens of kilometres between discrete outcrops (“outcrop-to-outcrop flow”) is consistent with the global heat flow data. This finding supports the proposition that outcrop-to-outcrop flow is the dominant mode of ridge flank hydrothermal circulation globally. An alternative model of ridge flank hydrothermal circulation in which fluid circulation occurs by local convection within isolated outcrops is also possible, and is probably the dominant mode of circulation in crust younger than 3-5 Myrs old, on average, where there is insufficient sediment cover to support the lateral pressure gradients required by outcrop-to-outcrop flow. Estimated crystallization temperatures of carbonate minerals in the crust suggest that, at some locations in the aquifer, local convective mixing may be restricted (i.e., the aquifer is poorly mixed), whereas the carbonate data for other locations cannot distinguish between a well mixed and a poorly mixed aquifer. A poorly mixed aquifer requires that vertical permeability is 1.5 - 2.5 orders of magnitude lower than horizontal permeability. This permeability anisotropy may arise from interlaying of different lithological units within the upper crust. / Graduate / 0388 / 0547 / brocka@uvic.ca