Dam failures and the following emptying of the reservoir are very seldom. But such catastrophes caused significant damages in the past. The related risk has to consider as high despite the high return period. The paper describes the development of hazard maps showing the dimension of inundation in the downstream region of the dam due to a potential failure. The needed data and possible used software for the dam break flood simulation were discussed. A dam break occurred in the catchment area of the Müglitz river in the Ore mountains during the flood 2002 is described. / Das Versagen einer Talsperre mit einer sich anschließenden Entleerung des Stauraumes ist sehr selten. Jedoch zogen solche Ereignisse in der Vergangenheit immer große Schäden nach sich, so dass trotz der geringen Eintrittswahrscheinlichkeit das Risiko als hoch einzuschätzen ist. Der Beitrag behandelt die Erstellung von Gefahrenkarten, die Auskunft darüber geben, wie groß die zu erwartende Überflutung infolge eines Bruches eines Absperrbauwerkes sein könnte. Dabei soll auf die zu ermittelnden Ausgangsdaten ebenso wie auf die zur Verfügung stehende Software zur Simulation der Ausbreitung von Talsperrenbruchwellen eingegangen werden. Als Fallbeispiel wird auf einen Dammbruch während des Hochwassers 2002 im Einzugsgebiet der Müglitz im Erzgebirge eingegangen.

The heavy rainfall event in August 2002 in Saxony/Germany caused the break of a flood retaining basin in a valley of the Erzgebirge Mountains. The rainfall event with ists hyrologic characteristics and dam break event were analysed and an outflow hydrograph was determing. The propagation of the dam break flood wave in the valleyas of the Briesnitz and Müglitz Rivers has been simulated. Calculated values were compared with some observed data.

Made available in DSpace on 2014-06-11T19:23:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-02Bitstream added on 2014-06-13T18:50:59Z : No. of bitstreams: 1 leite_lob_me_ilha.pdf: 7876959 bytes, checksum: 679218273f75952f4df0237622251b57 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Rompimentos de Barreira são fenômenos caracterizados por um campo de escoamento inicialmente represado e submetido nos instantes subseqüentes a uma liberação abrupta. Diversos modelos matemáticos e leis de comportamento reológico podem ser associados a este problema e cada um deles deve ser estudado e compreendido de maneira a predizer, a partir de testes físicos e numéricos, sua adequação à descrição da evolução espaço-temporal de frentes resultantes deste fenômeno, tipo ruptura de barragem, retendo água , rejeitos ou materiais de reologia complexa. O desenvolvimento de técnicas analíticas possibilitou entender de maneira impar o desenvolvimento desses fenômenos, porém, a difícil obtenção de dados que alcançassem consonância com aqueles obtidos experimentalmente, demonstrava a fragilidade desse tipo de análise perante a descrição de sistemas dinâmicos complexos. Sendo assim, optou-se pela tentativa de recriar estes fenômenos a partir de técnicas que utilizassem a manipulação de equações governantes completas. Sistemas contínuos podem ser analisados através de aproximações discretas, resultando em valores realísticos, muito próximos aos obtidos experimentalmente, e a capacidade computacional atual, permite diminuir sensivelmente os erros envolvidos, aumentando cada vez mais a consistência física destes métodos. Neste trabalho utilizou-se o software comercial ANSYS-CFX para simular os fenômenos de ruptura de barreira, configurando a reologia de dois materiais, o Carbopol 940 representando um material de reologia complexa (Herschel-Bulkley) e o Glicerol (Newtoniano), esses dados foram então confrontados com os obtidos experimentalmente através de um modelo em escala reduzida. Campos de velocidade, pressão e evolução temporal das frentes foram analisadas, verificando-se valores com grande consonância entre numérico e experimental, mostrando uma grande consistência física dos métodos utilizados / The Dam Break problem is a phenomenon characterized by a flow field initially dammed and submitted in the subsequent moments of an abrupt release. Various mathematical models and laws of rheological behavior may be associated with this type of problem and each must be studied and understood in order to predict from physical and numerical tests the temporal evolution of their fronts resulting from this phenomenon, type Dan Break problems, retaining water or rheology complex materials. The development of analytical techniques enabled the understanding the development of these phenomena, however, the difficulty to obtain a reach agreement data with those obtained experimentally, showed the fragility of this type of analysis to the description of complex dynamic systems. But, it was decided by attempt of recreate these phenomena from techniques that use the manipulation of complete government equations. Continuous systems can be analyzed by discrete approximations, leading to realistic values, very close to those obtained experimentally, and current computational capacity, enables to reduce the errors involved significantly, increasing the consistency of these physical methods. This work used the commercial software ANSYSCFX to simulate the phenomena of breaking the barrier, setting the rheology of two materials, the Carbopol 940 representing a material of complex rheology (Herschel-Bulkley) and glycerol (Newtonian), these data were then compared with those obtained experimentally using a model in scale. Fields of velocity, pressure and temporal evolution of the fronts were analyzed. Found very similar values between numerical and experimental simulations, showing the physical consistency of the methods used

Tsunamis are among the most terrifying and complex physical phenomena potentially affecting almost all coastal regions of the Earth. Tsunami waves propagate in the ocean over thousands of kilometres away from their generating source at considerable speeds. Among several other tsunamis that occurred during the past decade, the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami in Japan, considered to be the deadliest and costliest natural disasters in the history of mankind, respectively, have hit wide stretches of densely populated coastal areas. During these major events, severe destruction of inland structures resulted from the action of extreme hydrodynamic forces induced by tsunami flooding. Subsequent field surveys in which researchers from the University of Ottawa participated ultimately revealed that, in contrast to seismic forces, such hydrodynamic forces are not taken into proper consideration when designing buildings for tsunami prone areas. In view of these limitations, a novel interdisciplinary hydraulic-structural engineering research program was initiated at the University of Ottawa, in cooperation with the Canadian Hydraulic Centre of the National Research Council, to help develop guidelines for the sound design of nearshore structures located in such areas. The present study aims to simulate the physical laboratory experiments performed within the aforementioned research program using a single-phase three-dimensional weakly compressible Smoothed Particle Hydrodynamics (SPH) numerical model. These experiments consist in the violent impact of rapidly advancing tsunami-like hydraulic bores with individual slender structural elements. Such bores are emulated based on the classic dam-break problem. The quantitatively compared measurements include the time-history of the net base horizontal force and of the pressure distribution acting on columns of square and circular cross-sections, as well as flow characteristics such as bore-front velocity and water surface elevation. Good agreement was obtained. Results show that the magnitude and duration of the impulsive force at initial bore impact depend on the degree of entrapped air in the bore-front. The latter was found to increase considerably if the bed of the experimental flume is covered with a thin water layer of even just a few millimetres. In order to avoid large fluctuations in the pressure field and to obtain accurate simulations of the hydrodynamic forces, a Riemann solver-based formulation of the SPH method is utilized. However, this formulation induces excessive numerical diffusion, as sudden and large water surface deformations, such as splashing at initial bore impact, are less accurately reproduced. To investigate this particular issue, the small-scale physical experiment of Kleefsman et al. (2005) is also considered and modeled. Lastly, taking full advantage of the validated numerical model to better understand the underlying flow dynamics, the influence of the experimental test geometry and of the bed condition (i.e. dry vs. wet) is investigated. Numerical results show that when a bore propagates over a wet bed, its front is both deeper and steeper and it also has a lower velocity compared to when it propagates over a dry bed. These differences significantly affect the pressure distributions and resulting hydrodynamic forces acting on impacted structures.

The heavy rainfall event in August 2002 in Saxony/Germany caused the break of a flood retaining basin in a valley of the Erzgebirge Mountains. The rainfall event with ists hyrologic characteristics and dam break event were analysed and an outflow hydrograph was determing. The propagation of the dam break flood wave in the valleyas of the Briesnitz and Müglitz Rivers has been simulated. Calculated values were compared with some observed data.

Eigentümer und Betreiber von Anlgen mit einem großen Gefahrenpotential sind gehalten, den zuständigen Behörden Auskunft über mögliche Folgen eines Störfalles zu erteilen. Für den unwahrscheinlichen Fall des Bruches eines Absperrrbauwerkes können diesbezügliche Informationen erarbeitet werden.

La presente investigación se centra en la generación de mapas de peligro por la simulación del vertido de relaves por rotura de la presa del depósito de relaves en estado pulpa ubicada en el distrito de Chocó, en Colombia mediante un modelo hidrológico – hidráulico, y la posterior clasificación de los mapas de inundación y velocidad en niveles de peligrosidad. Este tipo de simulaciones requieren de un modelo numérico capaz de analizar y desarrollar el comportamiento de un flujo hiperconcentrado en la llanura de inundación aguas abajo. Las ecuaciones que controlan el movimiento de estos tipos de flujos son las aplicadas para fluidos no newtonianos, los cuales están controlados por los parámetros reológicos, como: viscosidad dinámica, esfuerzo de fluencia y la tasa de corte. Es por ello que se ha escogido el software FLO-2D el cual cuenta con facilidad de ingreso de datos y geometría, estabilidad de rutina computacional y la facilidad de lectura de archivos de salida. Los resultados obtenidos de la simulación en el distrito de Chocó muestran de manera didáctica la delimitación de zonas de riesgo de acuerdo a la clasificación de peligro en torno a velocidades y tirantes máximos. Eso nos permitió reconocer las estructuras que comprendidas en las zonas de alto riesgo. Estos mapas de peligro servirán como herramientas para evaluaciones de alcance social, ambiental y económico y la consideración y elección de medidas a corto, mediano y largo plazo, y de carácter tanto estructural, como no estructural. / This research focuses on the generation of hazard maps by simulating the discharge of tailings due to breakage of the dam of the pulp tailings deposit located in the Chocó district, in Colombia, using a hydrological-hydraulic model, and the subsequent classification of the flood and speed maps in danger levels. These types of simulations require a numerical model capable of analyzing and developing the behavior of a hyperconcentrated flow in the downstream floodplain. The equations that control the movement of these types of flows are those applied for non-Newtonian fluids, which are controlled by the rheological parameters, such as: dynamic viscosity, creep stress and the shear rate. That is why the FLO-2D software has been chosen which has ease of data entry and geometry, computational routine stability and ease of reading output files. The results obtained from the simulation in the Chocó district didactically show the delimitation of risk areas according to the hazard classification around maximum speeds and braces. This allowed us to recognize the structures included in high risk areas. These hazard maps will serve as tools for evaluations of social, environmental and economic scope and the consideration and choice of short, medium and long-term measures, both structural and non-structural. / Tesis

No / The standard shallow water equations (SWEs) model is often considered to provide weak solutions to the dam-break flows due to its depth-averaged shock-capturing scheme assumptions. In this study, an improved SWEs model using a recently proposed Surface Gradient Upwind Method (SGUM) is used to compute dam-break flows in the presence of a triangular hump. The SGUM allows the SWEs model to stably and accurately reproduce the highly complex shock currents caused by the dam-break event, as it improves the treatment of SWEs numerical source terms, which is particularly crucial for simulating the wet/dry front interface of the dam-break flow. Besides, an Incompressible Smoothed Particle Hydrodynamics (ISPH) modeling technique is also employed in this study to compare with the performance of the SGUM-SWEs model. The SPH method is totally mesh free and thus it can efficiently track the large free surface deformation. The ISPH approach uses a strictly incompressible two-step semi-implicit solution method. By reproducing a documented experimental dam-break flow, it has demonstrated that both model simulation results gave good agreement with the experimental data at different measurement locations. However, the ISPH simulations showed a better prediction of the dam-break peak wave building-up time, where its superiority was demonstrated. Furthermore, the ISPH model could also predict more detailed flow surface profiles across the streamwise flow direction and the velocity and pressure structures.

Yes / Based on the method of characteristics, an analytical solution for the one-dimensional shallow-water equations is developed to simulate the instantaneous dam-break flows propagating down a triangular wet bed channel in this study. The internal relationships between the hydraulic properties associated with the dam-break flow are investigated through the comparisons with the well-known analytical solutions for rectangular channels. Meanwhile, laboratory experiments are conducted in a prismatic, horizontal and smooth flume with a triangular cross-section. The non-intrusive digital image processing is applied for obtaining water surface profiles and stage hydrographs. Results show that the dam-break flow propagation depends on the dimensionless parameter defined as the ratio of initial tailwater depth over reservoir head. has significant effect on the dam-break wave in the downstream flooded area. For , the water surface profiles in the reservoir for different at a given time remains similar. For ≥ 0.5, extra negative waves occur in the reservoir, leading to the water surface undulations. Undular bores are generated at the dam site and propagate downstream. Time evolution of dam-break flows under three different reservoir heads is similar for the same . The inception of water surface profile change is earlier when the reservoir head is larger. The analytical model shows satisfactory agreement with the experimental results though some errors exist between the analytical solution and measurements due to the formation of extra negative waves, jet and undular bores. The similarities and discrepancies between the hydraulics in the triangular and rectangular channels are identified analytically in terms of the profiles of water depth, velocity, discharge, bore height and wave-front celerity with . The presented solution could be applied to predict the effect of wet bed condition on the dam-break wave in triangular channels, while laboratory measurement data could be used for validating analytical and numerical models. / National Natural Science Foundation of China (Grant No: 51879179), Sichuan Science and Technology Program (No. 2019JDTD0007) and Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1809)

Yes / Understanding of the characteristics of dam-break flows moving along a sloping wet bed can help to timely issue flood warning and risk mitigation. In this study, laboratory experiments are carried out in a large flume for a wide range of upstream water depth, bed slopes and tailwater depth. The water level is recorded and processed to calculate the mean velocity and wave celerity. Results show that the increase of the bed slope will significantly accelerate the wave-front celerity for the downstream dry bed, while the negative wave celerity will decrease. When water depth ratio α ≥ 0.3 (defined as the ratio of initial downstream water depth over the upstream water depth of dam), there are extra negative waves propagating towards the reservoir area after the flow has developed for a period of time. When α ≥ 0.6, there are the Favre waves propagating downstream. The water level and the mean velocity fluctuate due to the influence of the extra negative waves and the Favre waves. Such fluctuant frequency increases with the increase of the water depth ratio. The empirical formulas are obtained for the celerity of the first extra negative wave and the first downstream wave. The variation of wave-front height is very similar under three bed slopes investigated in this study, while the maximum wave-front height occurs when α = 0.2. The present study broadens the understanding of the effects of the bed slope and the tailwater level on the movement of the dam-break flows. Furthermore, experimental results are also compared with some analytical solutions. The validity of the assumptions made during the development of these analytical solutions and their limitations are discussed by comparing with the experimental measurements. / The National Natural Science Foundation of China (Grant No: 51879179), the Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1809) and Sichuan Science and Technology Program (No. 2019JDTD0007).