It is difficult to assess rangeland management practices at a hillslope scale because of the spatial and temporal variability of ecohydrological processes across a landscape. The Conservation Effects Assessment Project (CEAP) aims to provide a cost-effective method for quantifying benefits of conservation practices on rangelands. This study uses the Rangeland Hydrology and Erosion Model (RHEM) to develop a framework to assess rangeland management practices by quantifying sediment yield and runoff. Kaler Ranch, located in Eastern Arizona, was used as a study site because of their recently implemented rangeland conservation practices. Vegetation parameters were developed based on field data collected across the ranch and used to represent various rangeland management scenarios in RHEM. Peak flow and sediment yield rates were determined for each scenario using RHEM and were used as metrics to evaluate rangeland condition. RHEM provided an adequate method to evaluate the relative differences between upland rangeland management scenarios; however, it was less effective at evaluating changes in management practices within a riparian area.

<p>Abrasive waterjet (AWJ) machining is a complex, non-conventional machining process involving numerous input parameters including hydraulic, abrasive, mixing and cutting that must be accurately manipulated to guarantee precise cutting and quality. Currently, available models are empirical or require continuous calibration, or extensive experimental work. To reduce the calibration and experimental time required for accurate prediction of AWJ cutting, computational fluid dynamics (CFD) is being utilized to model the nozzle flow interaction; high pressure water is pushed through the orifice into the mixing chamber, pulling the abrasive into the flow and cohering in the focus tube. Initial research worked towards understanding the effect that input parameters - such as pressure, particle size and shape, focus tube length and volume fraction of air in fluid mixture - have on the velocity profile through the nozzle and upon exit to the atmosphere. Once understood, the CFD model can be utilized to vary mass-inlet, mixing head, orifice and focus tube dimensions to optimize velocity profile of abrasive material including magnitude and jet coherency. Primarily focused on pump pressure, which is limited by technology - an optimized AWJ nozzle will increase material removal rate and/or enhance cut quality without making changes to any other AWJM components.</p> <p>Utilizing the velocity output information from the CFD model, a depth of penetration erosion prediction model was generated. Based on methodology from Finnie, and modified by Hashish and ElTobgy, a multi-particle erosion model of an impacted work piece is developed. With an updated formulation for the specific cutting resistance of a work piece, dependent on particle velocity and nozzle traverse speed, the erosion prediction over the sixty-five different setups modelled and tested experimentally, reduced error on average 41.8%. Moreover, the development of this model created multi-layered surface plots, illustrating for quick reference, the erosion of a work piece for a given set of parameters albeit mass flow rate, pump pressure and traverse rate.</p> <p>Further, a database of quick reference guides, including variable input settings, nozzle types, garnet types and work piece materials can easily be developed. Finally, a new methodology for the leading edge of the waterjet is described and can be incorporated into the erosion simulation by making use of the ``top-hat`` profile generated in the CFD model. This would reduce reliance on model constants to account for secondary cutting, or when particles do not contribute to cutting but are simply entrained in the fluid flow.</p> <p>Both models demonstrated good correlation with experiments or literature. The use of these models will increase understanding of the complex abrasive waterjet process and reduce the need for costly experiments moving forward.</p> / Master of Applied Science (MASc)

The effect of eucalyptus forests in hidrossedimentologic processes has been little explored by the scientific community, which results in a database containing information related to these incipient effects, especially at the watershed scale. The monitoring and the mathematical modeling are recognized as effective tools of science to supply the lack of information, particularly in natural resource management, in the representation and prediction of these processes. In this sense, the aim of this study was to describe the monitoring data to assess effects of eucalyptus cultivation in the hidrossedimentological processes, to calibrate the input parameters and to verify the potential application of the Limburg Soil Erosion Model (LISEM) in the representation of watershed hydrological processes embedded with forest cover. The study was conducted in two forest watersheds located in Eldorado do Sul - RS, and the watershed has an area of 94.46 ha and drainage sub-watershed, which is embedded in the amount and terms of the watershed, has a drainage area of 38.86 ha. The hidrossedimentometrical monitoring began in February 2011 and was conducted within the limits of the watershed in two automatic sections, composed of linigraph, turbidimeters and pluviographs. This work has included monitoring over a period of six months from 02/16/2011 to 08/15/2011. The sediment yield was determined by multiplying the data of sediment concentration and flow. The model LISEM was calibrated from six different rain events. The model input parameters were obtained through surveys conducted in the watershed and literature data. To evaluate the model ability in representing the hydrological processes hydrographs measured in the watershed exutory were used. The monitoring results demonstrated that periods with higher rainfall volume presented a significant increase in peak flows in relation to the driest intervals, as well as an increase in the suspended sediments concentration in the watershed and in the sub-watershed. The events with greater rainfall intensity demonstrated that the smallest drainage area of the subwatershed generated faster answers in flow and sediment concentration. For the watershed, in most events occurred flood wave attenuation with least steeply sloping and lowest hydrograph peaks than the sub-watershed. Specifically, the sediment yield was 38.41 and 33.65 t km-2, during the six months of monitoring for the watershed and for the subwatershed, respectively. The magnitude of sediment yield was 0.77 t ha-1 yr-1 for the watershed and 0.67 t ha-1 yr-1 for the sub-watershed. The LISEM model was able to reproduce adequately the peak flow and direct runoff for the six events used for calibration. On the other hand, the peak time and shape of the hydrograph did not have adequate fit. / O efeito das florestas de eucalipto nos processos hidrossedimentológicos tem sido pouco explorado pela comunidade científica, o que resulta em banco de dados contendo informações incipientes relacionadas a esses efeitos, principalmente na escala de bacias. O monitoramento e a modelagem matemática são reconhecidos como eficientes ferramentas científicas para suprir a carência de informações, principalmente na gestão dos recursos naturais, na representação e na predição desses processos. Nesse sentido, objetivou-se com este estudo, descrever os dados do monitoramento, avaliar os efeitos dos cultivos de eucalipto nos processos hidrossedimentológicos, calibrar os parâmetros de entrada e verificar o potencial de aplicação do modelo Limburg Soil Erosion Model (LISEM) na representação dos processos hidrológicos de bacias hidrográficas embutidas, com cobertura florestal. O estudo foi desenvolvido em duas bacias hidrográficas florestais situadas em Eldorado do Sul RS, sendo que a bacia possui área de drenagem de 94,46 ha e a sub-bacia, que se encontra à montante e embutida em relação à bacia, possui área de drenagem de 38,86 ha. O monitoramento hidrossedimentométrico teve início em fevereiro de 2011 e foi realizado no exutório das bacias, em duas seções automáticas, compostas de linígrafos, turbidímetros e pluviógrafos. O presente trabalho contemplou o monitoramento durante um período de seis meses, de 16/02/2011 a 15/08/2011. Os resultados do monitoramento demonstram que os períodos com maior volume de precipitação apresentaram aumento significativo nos picos de vazão em relação aos intervalos mais secos, assim como aumento na concentração de sedimentos em suspensão, para a bacia e para a subbacia. Os eventos com maior intensidade máxima de precipitação demonstraram que a pequena área de drenagem e o relevo mais acentuado da sub-bacia geraram respostas rápidas na vazão e concentração de sedimentos. Para a bacia hidrográfica, na maioria dos eventos, ocorreu amortização da onda de cheia com hidrogramas menos íngremes e ocorrência após o pico de vazão da sub-bacia. A produção de sedimentos foi de 38,41 e 33,65 Mg km-2, durante os seis meses de monitoramento para a bacia e para a sub-bacia, respectivamente. O modelo LISEM foi calibrado a partir de seis eventos de chuva. Os parâmetros de entrada utilizados para o modelo foram obtidos por meio de levantamentos realizados na bacia e de dados da literatura. Para avaliar a capacidade do modelo em representar os processos hidrológicos, foram utilizados hidrogramas medidos no exutório da bacia. A análise estatística aplicada foi o teste BIAS (Erro (%)) para os parâmetros vazão de pico, escoamento superficial direto e tempo de pico. Para avaliar a eficiência do modelo em reproduzir adequadamente o formato dos hidrogramas, foi utilizado o Coeficiente de eficiência Nash-Sutcliffe (COE) para os seis eventos utilizados na calibração. O modelo LISEM foi capaz de reproduzir adequadamente a vazão de pico e o escoamento superficial direto para os seis eventos utilizados na calibração, indicado pelos baixos erros percentuais. Por outro lado, o tempo de pico e a forma do hidrograma não apresentaram ajuste adequado, indicado pelos elevados erros e valores negativos para o erro e para o COE, respectivamente.

Made available in DSpace on 2015-05-14T12:09:24Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2295007 bytes, checksum: 52298de3dc8f0b897353a1ec81ae8e71 (MD5) Previous issue date: 2011-11-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The degradation of water quality and quantity are among the major environmental problems, which the society is facing today. Environmental managers use computer modeling to simulate and to better understand the natural phenomena that occur in watersheds, in order to assist the planning of the use and preservation of natural resources. Among several existing models, there is the WESP model (Watershed Erosion Simulation Program), which wasdeveloped in order to simulate the hydrological response of small basins. Considering these and other facts, the aim of this study is to evaluate the performance of two optimization algorithms to calibrate the WESP model, in order to simulate the runoff-erosion processes within the semiarid area of Paraiba state. This calibration was performed using the optimization methods RPS (Repulsive Particle Swarm) and DE (Differential Evolution),expecting to find the best set of parameters to be used in the modeling. Subsequently, it was performed a comparison between the observed and calculated runoff, and between the observed and calculated sediment yield. The results show that the automatic calibration routine RPS obtained a more satisfactory set of parameters, and converged with a reduced number of interactions, when compared to the DE optimization method. / A degradação qualitativa e quantitativa da água está entre os grandes problemas ambientais enfrentados pela sociedade atual. Gestores ambientais utilizam a modelagem computacional para simular e melhor compreender os fenômenos naturais que ocorrem nas bacias hidrográficas, auxiliando no planejamento de uso e preservação dos recursos naturais. Entre vários modelos existentes, o WESP (Watershed Erosion Simulation Program) foi desenvolvido com a finalidade de simular a resposta hidrológica de pequenas bacias hidrológicas. Considerando estes e outros fatos, o objetivo do presente estudo é avaliar o desempenho de dois algoritmos de otimização na calibração do modelo WESP para simulação de processos hidrossedimentológicos no semiárido paraibano. Esta calibração foi realizada utilizando o método de otimização RPS (Repulsive Particle Swarm) e o método de otimização DE (Differential Evolution), na expectativa de encontrar o melhor conjunto de parâmetros usados na modelagem. Posteriormente, foi realizada a comparação entre as lâminas escoadas observadas e calculadas, e também a comparação dos resultados da produção de sedimentos gerados por estes escoamentos com os valores da produção observada. Os resultados mostram que a rotina de calibração automática RPS obteve um conjunto de parâmetros mais satisfatório, além de convergir com uma quantidade reduzida de interações em comparação com o método de otimização DE.

Fluid jet polishing (FJP) is a new advanced polishing technology that finds applications in many industries, especially in the optics industry. With the broad application of various surfaces in optics, the sub-micrometric scale and the nanometric surface roughness accuracy are major challenges. Fluid jet polishing is a technology developed from abrasive water jet machining. This technology is a water jet cutting technology, which uses high-pressure flow to cut/remove materials. In this thesis, the working principle, and simulations, as well as verification of fluid jet polishing are thoroughly investigated. The verification of fluid jet polishing in this thesis includes velocity distribution and material removal derivations. The amount of material removed is directly related to the impact velocity of a particle with a surface, which helps define its abrasive particle velocity. During polishing, the particles travel in a solution called slurry. Due to the relatively similar velocity of the particles and the slurry, the particles and the slurry are assumed to be traveling at the same rate. In this thesis, three specific examples are investigated through the creation of an advanced model using FLUENT, a computational fluid dynamics software. The model simulates the particle path during the fluid jet polishing process, and this thesis compares the simulation results to prior analytical and experimental results. The results indicate that the fluid jet polishing erosion area at a particular location is axisymmetric when the 2D cross-section shape is investigated. As the impingement angle of the fluid jet is reduced, the center dead area, where no polishing is observed, approaches zero. vii Additionally, the horizontal component of the velocity vector initially increases then decreases as one moves away from the center stagnation point. Finally, this thesis demonstrates that the erosion depth into the surface that is polished increases when the working pressure of the fluid is increased. This thesis finds that when the distance between the fluid jet and the workpiece is 7 mm, material removal is maximum.

The erosion and transport of fertile topsoil is a serious problem in the U.S., Australia, China and throughout Europe. It results in extensive environmental damage, reduces soil fertility and productivity, and causes significant environmental loss. It is as big a threat to the future sustainability of global populations as climate change, but receives far less attention. With both chemicals (fertilizers, pesticides, herbicides) and biological pathogens (bacteria, viruses) preferentially sorbing to silt and clay sized soil particles, estimating contaminant fluxes in eroded soil also requires predicting the transported soils particle size distribution. The Hairsine-Rose (HR) erosion model is considered in this thesis as it is one of the very few that is specifically designed to incorporate the effect of particle size distribution, and differentiates between non-cohesive previously eroded soil compared with cohesive un-eroded soil. This thesis develops a new extended erosion model that couples the HR approach with the one-dimensional St Venant equations, and an Exner bed evolution equation to allow for feedback effects from changes in the local bed slope on surface hydraulics and erosion rates to be included. The resulting system of 2I +3 (where I = number of particle size classes) nonlinear hyperbolic partial differential equations is then solved numerically using a Liska-Wendroff predictor corrector finite difference scheme. Approximate analytical solutions and series expansions are derived to overcome singularities in the numerical solutions arising from either boundary or initial conditions corresponding to a zero flow depth. Three separate practical applications of the extended HR model are then considered in this thesis, (i) flow through vegetative buffer strips, (ii) modelling discharge hysteresis loops and (iii) the growth of antidunes, transportational cyclic steps and travelling wave solutions. It is shown by comparison against published experimental flume data that predictions from the extended model are able to closely match measurements of deposited sediment distribution both upstream and within the vegetative buffer strip. The experiments were conducted with supercritical inflow to the flume which due to the increased drag from the vegetative strip, resulted in a hydraulic jump just upstream of the vegetation. As suspended sediment deposited at the jump, this resulted in the jump slowly migrating upstream. The numerical solutions were also able to predict the position and hydraulic jump and the flow depth throughout the flume, including within the vegetative strip, very well. In the second application, it is found that the extended HR model is the first one that can produce all known types of measured hysteresis loops in sediment discharge outlet data. Five main loop types occur (a) clockwise, (b) counter-clockwise, (c,d) figure 8 of both flow orientations and (e) single curve. It is clearly shown that complicated temporal rainfall patterns or bed geometry are not required to developed complicated hysteresis loops, but it is the spatial distribution of previously eroded sediment that remains for the start of a new erosion event, which primarily governs the form of the hysteresis loop. The role of the evolution of the sediment distribution in the deposited layer therefore controls loop shape and behavior. Erosion models that are based solely on suspended sediment are therefore unable to reproduce these hysteretic loops without a priori imposing a hysteretic relationship on the parameterisations of the erosion source terms. The rather surprising result that the loop shape is also dominated by the suspended concentration of the smallest particle size is shown and discussed. In the third application, a linear stability analysis shows that instabilities, antidunes, will grow and propagate upstream under supercritical flow conditions. Numerical simulations are carried out that confirm the stability analysis and show the development and movement of antidunes. For various initial parameter configurations a series of travelling antidunes, or transportational cyclic steps, separated by hydraulic jumps are shown to develop and evolve to a steady form and wave speed. Two different forms arise whereby (a) the deposited layer completely shields the underlying original cohesive soil so that the cohesive layer plays no role in the speed or shape of the wave profile or (b) the cohesive soil is exposed along the back of the wave such that both the non-cohesive and cohesive layers affect the wave profile. Under (a) the solutions are obtained up to an additive constant as the actual location of the boundary of the cohesive soil is not required, whereas for (b) this constant must be determined in order to find the location on the antidune from where the cohesive soil becomes accessible. For single size class soils the leading order travelling wave equations are fairly straightforward to obtain for both cases (a) and (b). However for multi-size class soils, this becomes much more demanding as up to 2I + 3 parameters must be found iteratively to define the solution as each size class has its own wave profile in suspension and in the antidune.

L’objectif de cette thèse est la détermination des causes du phénomène d'érosion marine, et la production de propositions d'orientation pour la protection de la plage de l’Almanarre. L'étude commence par la collecte et l'analyse de toutes les données disponibles, pour trouver des règles d’évolution du tombolo de Giens. Puis, le logiciel de modélisation MIKE a été appliqué pour confirmer l'hypothèse et à obtenir une meilleure connaissance de la dynamique à l’œuvre au tombolo Ouest. Ensuite, nous avons couplé des facteurs simultanément : les houles, les courants côtiers, et les transports des sédiments pour les différents régimes de houle et de vent dans MIKE 21. Enfin, la possibilité de stabiliser le tombolo Ouest est discutée pour donner des suggestions sur les choix de solutions adaptées. / The objective of this thesis is the determination of the causes of sea erosion phenomenon, and the production of policy proposals for the protection of the beach. The study begins with the collection and analysis of all available data, to find evolution rules of tombolo of Giens. Which aims to explain how the hydrodynamic processes and sediment transport occur. Then MIKE modeling software was applied to confirm the hypothesis and get a better understanding of the dynamics at work in the Western tombolo. Then, we coupled factors simultaneously: waves, coastal currents and sediment transport for different regimes of wave and wind in MIKE 21. Finally, the possibility of stabilizing the Western tombolo is discussed to give suggestions on the choice of solutions.