Hydrological and hydraulic effects of urban development is one of the key issues of study for improved water management. The addition of impervious surfaces to once pervious land and re-routing open channels and flow paths can cause flooding or declining water levels within a watershed. Many studies of these issues have found that there can be multiple factors causing hydrological and hydraulic impacts, and it can be hard to analyze and develop effective solutions without appropriate drainage software packages. However, there are multiple software packages available for use, and determining the correct one to use for a specific challenge can often be a case by case decision. This study compares two drainage software packages: Autodesk Storm and Sanitary Analysis (SSA), and the Army Corps of Engineers Hydrologic Modeling System (HEC-HMS). Each of these software packages are used to create a model of the Andrée Clark Bird Refuge in Santa Barbara, CA. The models analyze both current conditions and anticipated system response under the assumption that historical runoff from a previously re-routed creek and corresponding watershed are restored. Each model was used to determine the minimum cumulative rainfall that causes circulation of the water body, a maximum cumulative rainfall that causes flooding on site, and response under both routing scenarios to a 2-year frequency storm. Results from both models are compared for uniformity, and application of each model is reviewed for its efficacy as a design tool for this sort of hydrological and hydraulic analysis.

With the coming of Generation IV systems, there is a need for thermal-hydraulic codes to model such advanced reactors. Codes for High Temperature Gas-cooled Reactors (HTGRs) already exist, but often suffer from insufficient validation and little user experience. Therefore, some existing codes created for Light Water Reactors are updated with HTGR related features. In this study, the feasibility of providing the TRACE thermal-hydraulics code with those features is analysed. Two models were used, one of a pebble bed core, one of a prismatic block reactor. For this purpose the effective conductivity test of the High Temperature Test Unit was taken as a benchmark for the pebble bed core. For the prismatic block reactor a model of the GEMINI+ reactor was created. This would allow to simulate not only steady state, but also Depressurised Loss of Forced Cooling scenarios. For both models the effective conductivity is known to play a major role and, consequently, a model to incorporate such feature was developed and implemented within TRACE's control system module. Results show that TRACE has a good potential for HTGR simulation, but currently available models still provide unstable solutions. It is concluded that TRACE needs additional adjustments in order to be employed for HTGR safety analyses in the future. / Med fjärde generationens system på ingång, finns det ett behov av termisk-hydrauliska koder för att modellera sådana avancerade reaktorer. Koder för gaskylda högtemperaturreaktorer (HTGR) finns redan, men lider ofta av otillräcklig validering och liten användarupplevelse. Därför uppdateras vissa befintliga koder som skapats för lättvattenreaktorer med HTGR-relaterade funktioner. I denna studie analyseras möjligheten att tillhandahålla TRACE termisk-hydraulisk kod med dessa funktioner. Två modeller användes, den ena av en pebble-bed reaktor, den andra av en prismatisk blockreaktor. För detta ändamål togs det effektiva konduktivitetstestet för högtemperaturtestenheten som ett riktmärke för pebble-bedens härd. För den prismatiska blockreaktorn skapades en modell av GEMINI+-reaktorn. Detta skulle göra det möjligt att simulera inte bara steady state, utan även scenarier med trycklös förlust av forcerad kylning. För båda modellerna är den effektiva konduktiviteten känd för att spela en stor roll och följaktligen utvecklades och implementerades en modell för att införliva en sådan funktion inom TRACEs kontrollsystemmodul.. Resultaten visar att TRACE har en god potential för HTGR-simulering, men för närvarande tillgängliga modeller ger fortfarande instabila lösningar. Slutsatsen är att TRACE behöver ytterligare justeringar för att kunna användas för HTGR-säkerhetsanalyser i framtiden.

Climate model projections revealed a likelihood of increased frequency and magnitude of hydrological extremes in future climate due to continued emissions of greenhouse gases. Considering that it will significantly affect the planning and designing of flood management systems, for instance stormwater management infrastructures, and designation of flood risk area, it is vital to investigate the climate change impact on the hydrological processes and respective consequences on the flood management systems. The primary objective of this research is to investigate the climate change impact at watershed scale, and the goal was achieved by investigating the climate change impact on hydrological processes, assessing the potential impact of changed hydrological processes on drainage systems and flooding scenarios. The study area in this research includes Spencer Creek watershed, West Central Mountain drainage area and Clearview Creek drainage area located in Southern Ontario, Canada. The climate projections used in this study were the North American Regional Climate Change Assessment Program (NARCCAP) climate simulations based on SRES A2 scenario. For Spencer Creek watershed, NARCCAP provided eight RCM+GCM pair’s climate projections were bias- corrected, and used as input in a calibrated hydrological model HBV to simulate flows at the outlet of the watershed. A significant improvement of bias-corrected precipitation and temperature was revealed by Brier and Rank Probability Skill Score. The results revealed an increase in winter daily average flows and decrease in other seasons, and approximately 13% increase in annual evapotranspiration, and an increase in high flows and decrease in low flows under future climate conditions. Consequences for changed hydrological processes on urban stormwater management systems were investigated for West Central Mountain drainage area. Design storm depths were calculated by using the best fitted distribution among twenty seven distributions and by applying delta change factor. The PCSWMM model was used for flow simulation and hydraulic analysis for the storm-water management system, specifically storm sewer and detention pond. The assessment results indicate that the performance of the detention pond as well as the storm sewer network will deteriorate under future climate condition as design storm depths increase. For Clearview Creek drainage area, a single event hydrologic model Visual OTTHYMO and hydraulic analysis tool HEC-RAS were used to simulate flow and water level. The results revealed an increase of peak flows ranging from about 26 % to 64% for 2yr and 100yr return periods at the outlet of the Creek, and an average increase of water surface elevation and extents by 30 cm and 37.1 m, respectively, for a 100 year return period flood. Finally, non-stationary frequency analyses for design storm calculation were recommended for more robust and accurate investigation of climate change impact. / Thesis / Doctor of Philosophy (PhD)

Climate change and urbanization causes the increasing challenges of flooding in urban watersheds. Even the rivers identified as non-vulnerable are causing catastrophic damage due to heavy flooding. So, several satellite and radar-based precipitation data are considered to study the watersheds with no gauge station or need recent precipitation data. Weather Radar (NEXRAD)arch, the accuracy of satellite-based precipitation data, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Climate Data Record (PERSIANN-CDR), and radar-based precipitation data, Next Generation Weather Radar (NEXRAD), is evaluated in rainfall-runoff simulation considering Hydrological Engineering Centre-Hydrologic Modeling System (HEC-HMS) and Personal Computer Storm Water Management Model (PCSWMM), respectively.The primary research proposes a framework for modeling the rainfall-runoff process using PERSIANN-CDR and a floodplain map in an ungauged urban watershed. The one-dimensional Hydrologic Engineering Centre-River Analysis System (HEC-RAS) model generates a flood inundation map for the pertinent flooding occurrences from the acquired peak hydrograph, providing a quantifiable display of the inundation extent percentage. The second research uses the PCSWMMs to show the extent of flooding. It also employs the compromise programming method (CPM) to rank the most critical sub-catchments based on three parameters: slope, surface area, and impervious area. Three low-impact development (LID) strategies over the watershed determine the best flood management option. Therefore, the overall study presents a comprehensive framework for flood management in urban watersheds that integrates satellite precipitation data, hydrologic modeling, and LID strategies. The framework can provide an accurate flood-prone zone and help prioritize critical sub-catchments for flood management options. The study proposes using HEC-HMS and PCSWMM models to simulate and analyze interactions between rainfall, runoff, and the extent of the flood zone. Furthermore, LID can be applied to reduce flooding in urban watersheds. Overall, the framework can be helpful for policymakers and system managers to build the watershed's resilience during catastrophic flooding events caused by climate change and urbanization.

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The effects of appendages on flow characteristics and scalar mixing in gap-connected twin-subchannel geometries has been assessed. The assessment considers a symmetric, rectangular compound channel geometry connected by a single rectangular gap using computational fluid dynamics (CFD). Detailed numerical models (geometry and turbulence), characterizing the full test section from a reference experimental study, are generated and validated against measurements. Time varying details of the gap induced periodic structures and appendage induced vortices are captured through calculations in an unsteady Reynolds averaged Navier-Stokes (RANS) framework coupled with the Spalart-Allmaras (SA) turbulence model closing the RANS equations. Companion simulations are performed at each of two Reynolds numbers (2690 and 7500), one with and one without a gap-centered appendage. The appendage size modelled is representative of CANDU endplates. The appendage effects on flow characteristics and mixing are isolated through comparison of the associated simulations. In the absence of appendages, fluid exchange between subchannels is dominated by quasi-periodic flow pulsations through the gap formed due to flow instability in the near gap region. Without a gap-centered appendage, the magnitude, frequency, and structure length of the gap flow pulsations are well predicted by the model at both Reynolds numbers. The total tracer transfer between subchannels is reasonably well predicted for Re = 2690 (within approximately 17% of the experimental value). The model fails to capture the measured increase in scalar transfer through the gap with increased Reynolds number, underpredicting scalar mixing by 55% at Re = 7500. An argument is presented that the use of an isotropic turbulence model in the channel (SA), which precludes the development of channel secondary flows, is the source of the discrepancy between modelled and measured mixing at Re = 7500. Appendages, such as those introduced by end plates or bearing pads in CANDU fuel bundles, augment the exchange process between subchannels. With an appendage representative of a CANDU fuel bundle endplate introduced into the gap region, crossflow velocity and frequency are predicted to increase immediately downstream of the appendage due to flow diversion and vortex shedding. The higher local frequency is shown to be consistent with the vortex shedding frequency calculated for a stationary rectangular cylinder at the gap conditions. Further downstream, gap induced instabilities begin to re-establish as the dominant contributor to crossflow pulsations although they are not fully recovered by the test section exit. Mixing is augmented more by the appendage with increasing Reynolds number for the range examined. / Thesis / Master of Applied Science (MASc) / The fuel bundle and pressure tube assembly in the core of a CANDU reactor forms an intricate web of subchannels of varying geometries with interconnecting gaps. Heat generated within the fuel bundles is removed by coolant flowing through the pressure tube and within the bundle subchannels. Although flow is nominally axial along the length of the rod bundles, coolant is free to move between subchannels through the gaps by a variety of mechanisms. Detailed fluid flow in these rod bundle geometries is a complex 3D phenomenon, strongly affected by fluid turbulence and flow instabilities associated with the subchannel geometry. This flow is investigated in the current study and extended to include the effect of appendages, which hold the fuel rods in place, to determine their impact on mixing along the length of the bundle. Particular applications of the results of this study are in the areas of nuclear reactor performance and safety. The extent of coolant exchange between subchannels affects the local subchannel flow and temperature and, as a result, local cooling at the fuel element surfaces. Fuel element cooling is a principal component of reactor analysis under both normal operating conditions and postulated accident scenarios.

yes / This paper presents field measurements in which dye solute was injected into coastal sand to investigate contaminant advection in intertidal beach sand. The measurements show the pathways of a contaminated plume in the unsaturated zone during both the flood and ebb tides. A prescribed amount of dye tracer solution was directly injected through the topsoil, with average porosity 0.3521±0.01, at predetermined locations of the River Mersey’s outer estuarial beach during ebb-tide. The injected dye was monitored, sampled and photographed over several tidal cycles. The distinctive features of the plume (full two dimensional cross-sections), sediments and water-table depth were sampled in-situ, close to the injection point (differing from previous contaminant monitoring tests in aquifers). The advective movement is attributed to tidal impact which is different from contaminant transport in aquifers. The experimental results show that plumes have significantly large spatial variability, diverging upwards and converging downwards, with a conical geometric shape which is different from the usual spherical/elliptical shape reported in literature. The mean vertical motion of the plume reaches three times the top-width within ten tidal cycles, exceeding the narrow bottom-width by a factor of order 2. The observed transport features of the plume within the beach sand have significant relevance to saltwater intrusion, surface water and groundwater quality. The field observations are unique and can serve as a valuable benchmark database for relevant numerical studies. / China Ministry of Science and Technology 973 program (2014CB745001), Special Program of future development in Shenzhen (201411201645511650) and Shenzhen Key Laboratory for Coastal Ocean Dynamic and Environment（ZDSY20130402163735964).

<p>Amidst the increasing need to improve efficiency of fluid power systems for off-road vehicles, different architectures have been proposed in literature to reduce system throttling losses. Among the most cited ones, are architectures based on the use of common-pressure rails (CPR), which in some cases have been combined with multi-chamber cylinders to further reduce power losses. This kind of solution appears to be particularly attractive in systems with several actuators with many instances of overrunning loads, such as in earthmoving machines. In this scenario, a basic question arises concerning the maximum amount of energy that can be saved by adding extra pressure rails and/or cylinder chambers. Answering this question can be challenging given that many parameters such as cylinder areas, pressure levels and both actuator and supervisory level controls can affect the results for a given application. This work investigates energy savings potential of different architectures based on the previously mentioned concept. Based on the results of this investigation, a novel architecture combining multi-pressure rails and multi-chamber cylinders is proposed and investigated. The system is sized and simulated for the study case of an excavator. This work addresses controllers design, from the supervisory level power management control to the local cylinder actuation system. In addition, special care is taken in the area selection of the multi- chamber cylinder, with factors such as manufacturing cost and reliability being considered. The proposed design procedure allows the design of compact and efficient three-chamber cylinders on a wider range of applications. Results show the potential for power consumption reduction of up to 31% when compared to state-of-the-art machines available in the market. Additionally, the proposed cylinder design optimization allows a reduction of up to 25% in cylinder weight when compared to other design methods for multi-chamber cylinders. Within this scope, an experimental setup is designed for proof of concept of the proposed hydraulic circuit and cylinder control methods, with laboratory tests validating the feasibility of the proposed system. Test results demonstrated the ability of the proposed controller in efficiently controlling pressures within the actuator, while delivering stable speed tracking performance. Experiments also demonstrated the system capability in recovering energy and validated the expectation of obtaining hydraulic actuation with low pressure drop across control valves.</p>

Agricultural land use near streams frequently results in long-term disturbance to woody riparian vegetation and an alteration of reach scale geomorphic structure. Such disturbances often result in increased fine sediment input to the stream along with direct changes in channel structure. The study described here was designed to quantify stream geomorphic changes associated with agriculture and their influence on reach scale transient storage hydraulics and sediment biological function. Six small streams in the Appalachian Mountains of western North Carolina were selected to compare 3 reaches with active near-stream agriculture to 3 forested reference reaches. The study site categories differed significantly in many structural and hydraulic properties including slope, sinuosity, sediment size, and transient storage extent. However, differences cannot be attributed to land use alone. Distinct disparity in slope suggests that many of the categorical differences between stream types may also reflect valley scale structure. Despite these larger scale controls, the abundance of suspendable fines varied substantially among agricultural stream substrates, possibly due to varied land-use practices. Suspendable fine sediments and valley slope explained 91 % of variability in transient storage exchange, and abundance of inorganic fine sediments explained 77 % of variability in sediment microcosm nitrate production. This study supports conclusions that reach-scale influence of fine sediments occurred within the context of larger-scale valley structure, with implications on stream hydraulics and biogeochemistry. / Master of Science