Les espèces de poissons migrateurs (saumon atlantique, Salmo salar, en particulier) requièrent des conditions thermiques bien spécifiques. Ils sont très sensibles aux températures de l’eau et aux fortes variations estivales. Sur les trente dernières années, l’étude menée sur la Garonne (France) révèle une augmentation des températures estivales associée à un allongement de la durée des périodes chaudes. L’impact de cette modification du régime thermique sur la survie et la reproduction des espèces migratoires est également mis en évidence. Cette étude est menée sur un tronçon de Garonne, situé entre l’amont de Toulouse et l’amont de la retenue deMalause. Ce secteur est fortement touché par cette problématique avec en moyenne 2°C d’écart entre l’amont et l’aval et des températures supérieures à 25°C régulièrement atteintes. Le régime hydrologique de ce tronçon est fortement déficitaire (selon le SDAGE Adour-Garonne), la sensibilité au flux de surface est forte à cause de son lit large et peu profond, les pressions anthropiques sont importantes, ce sont autant de pistes dont l’impact sur le régime thermique est étudié. Une large collection de données hydrologiques et climatiques est exploitée afin de déterminer les processus en jeu dans l’évolution du régime thermique de ce tronçon de fleuve. Des études en tendances et corrélations et des modèles statistiques permettent de mettre en évidence d’une part la relation forte qui existe entre les températures de l’air et les températures de l’eau et d’autre part l’importance des faibles débits durant les périodes estivales. L’estimation des moyennes journalières de température de l’eau à Malause au moyen de modèles statistiques et déterministes donne de bons résultats pour les températures élevées ainsi que pour les franchissements de seuils liés aux conditions de migrations des amphilalins.Enfin un modèle numérique monodimensionnel de résolution de l’équation de transport thermique et des équations de St-Venant est développé. La physique du modèle tant au niveau hydraulique (prise en compte de fortes variabilités de pente, d’ouvrages, etc.) que thermique (apports latéraux, flux de surfaces, flux de conduction avec le lit) permet d’analyser l’évolution des différents flux qui participent au réchauffement du cours d’eau. Une évolution future à l’aide des sorties des modèles de l’IPCC est explorée et des méthodes éventuelles de restauration des conditions de températures favorables pour les espèces piscicoles sont analysées. / Fish species with strong thermal requirements (i.e. Atlantic salmon) are very sensitive to temperature evolution and particularly to large increases. An investigation conducted on the Garonne River (France) during the last three decades revealed global water warming along with an increase of the high temperature period duration. Large impact of this evolution on the survival and breeding of migrating fish species was also reported. Study was thus conducted on a specific reach of the Garonne River located between the immediate upstream of Toulouse and the upstream of the Malause dam. The issue of water temperature warming is particularly relevant on this reach, with an average increase of 2°C between upstream and downstream and temperatures above 25°C frequently reported. Potential causes are numerous: drastic low-flow regime (quoting SDAGE Adour-Garonne), impacts of surface fluxes that are important due to bed shape (wide and shallow), anthropogenic impacts, etc. Large amount of climatic and hydraulic data are used to make a clear determination of the processes involved in the thermal regime evolution of this reach. Trend and correlation analyses and use of statistical models indicate the strong relation between stream temperature and climate. Low flows also seem to be related to water temperatures during summer periods. Statistic and deterministic models give good results in estimating high daily mean water temperatures (RMSE ranging from 0.99°C to 1.22°C) and predicting water temperatures threshold crossings related to the migrating conditions of Atlantic salmon.Finally, a one-dimensional numerical model that solves both shallow water and thermal equations is developed. Both the formulation of the St-Venant equations (high variability in slope, gates …) and the phenomena taken into account in the water temperature model (lateral influx, surface fluxes, bed conduction …) allows studying the evolution of fluxes driving water temperature evolution. Future evolution of the water temperature at the 2050 horizon is also evaluated using IPCC models output and potential solutions to restore favorable stream temperatures conditions for fishes are analyzed.

Although the spectral technique is frequently used for the horizontal discretization in global atmospheric models, it is not common in limited area models (LAMs) because of the non-periodic boundary conditions. We apply the Haugen-Machenhauer extension technique to a regional three-layer shallow-water model based on double Fourier series. The method extends the time-dependent boundary fields into a zone outside the integration area in a way that periodic fields are obtained. The boundary fields necessary for the regional model simulations are calculated in advance by a global simulation performed. In contrast to other studies, we use exactly the same numerical model for the global and the regional simulation, respectively. The only difference between these simulations is the model domain. Therefore, a relatively objective measure for errors associated with the extension technique can be obtained. First, we compare an analytic stationary non-linear and non-periodic solution of the governing model equations with the spectral LAM solution. Secondly, we compare the time evolution of pressure and fiow structures during a westerly fiow across an asymmetric large-scale topography in the global and regional model domains. Both simulations show a good agreement between the regional and the global solutions. The rms-errors amount to about 2 m for the layer heights and 0.2 ms-1 for the velocity components in the mountain fiow case after a 48 h integration period. Finally, we repeat this simulation with models based on 2nd and 4th order finite differences, respectively, and compare the errors of the spectral model version with the errors of the grid point versions. We demonstrate that the high accuracy of global spectral methods can also be realized in the regional model by using the Haugen-Machenhauer extension technique. / Obwohl spektrale Techniken häufig zur horizontalen Diskretisierung in globalen Atmosphärenmodellen genutzt werden, sind sie aufgrund der nicht-periodischen Randbedingungen in Regionalmodellen nicht üblich. Wir verwenden das Erweiterungsverfahren von Haugen und Machenhauer in einem Flachwassermodell mit drei Schichten, das auf doppelten Fourier-Reihen basiert. Das Verfahren setzt die zeitabhängigen Randfelder so in einen Bereich außerhalb des Integrationsgebiets fort, daß man periodische Randbedingungen erhält. Die für die Simulationen mit dem Regionalmodell benötigten Randfelder werden mittels einer zuvor durchgeführten globalen Simulation berechnet. Im Gegensatz zu anderen Untersuchungen verwenden wir genau das gleiche Modell für die globale und die regionale Simulation. Der einzige Unterschied zwischen den beiden Simulationen ist das Modellgebiet. Dadurch erhält man ein relativ objektives Maß für die Fehler, die durch die Anwendung des Erweiterungsverfahrens entstehen. Als ersten Test vergleichen wir zunächst eine analytische, stationäre, nicht-lineare und nicht-periodische Lösung der Modellgleichungen mit der spektralen Lösung des Regionalmodells. Zweitens vergleichen wir die zeitliche Entwicklung von Druck- und Strömungsmustern während einer westlichen Strömung über eine unsymmetrische, großskalige Topographie im globalen bzw. regionalen Modellgebiet. Beide Simulationen zeigen eine gute Übereinstimmung der globalen und regionalen Lösungen. Die rms-Fehler betragen ungefähr 2 m für die Schichthöhen und 0.2 ms-1 für die Geschwindigkeitskomponenten bei der Bergüberströmungssimulation nach einer Integrationszeit von 48 h. Darüberhinaus wiederholen wir diese Simulation mit auf Finiten Differenzen 2. bzw. 4. Ordnung basierenden Modellen und vergleichen die Fehler der spektralen und der Gitterpunktversionen. Wir zeigen, daß die hohe Genauigkeit der globalen spektralen Methoden durch die Anwendung des Erweiterungsverfahrens von Haugen und Machenhauer auch auf das regionale Gebiet übertragen werden kann.

Nous nous intéressons à l’étude théorique et numérique de plusieurs modèles d’écoulement (Saint-Venant, multicouches, milieux poreux stationnaires et non stationnaires) et de leurs applications à l’optimisation de formes de certains ouvrages hydrauliques. Nous explorons le caractère bien posé des systèmes, nous dérivons un système adjoint lié à chaque modèle.Une méthode de pénalisation est utilisée pour relaxer la contrainte d’incompressibilité de la vitesse.Nous exprimons le gradient de forme en fonction de la vitesse u comme variable d’état, des variables adjointes, et le vecteur unité normal au bord du domaine.Nous adoptons une méthode d’éléments finis discrète pour approcher la solution du problème pénalisé et établissons des estimations à priori afin de prouver la convergence de la solution approchée vers la solution du système non perturbé.Le problème d’optimisation est implémenté en utilisant la méthode adjointe continue et la méthode d’éléments finis. / We are interested in the theoretical and numerical study of different flow models (shallow water system, multilayer, stationary and non stationary porous media) and their applications to the shape optimization of some hydraulic structures.We explore the well-posedness of the models and derive the adjoint equations related to each system.A penalty method is used to relax the incompressibility constraint for the velocity. We express the shape gradient of the cost function in terms of the velocity value as a state variable, the adjoint variables and the unit normal vector to the boundary of the domain.We propose a discrete finite element method to approximate the solution for the penalizedproblem and establish a priori estimates to prove the convergence of the approximate solution to the solution of the non perturbed problem. Error estimates for the velocity and the pressure are established.The optimization procedure is implemented using the continuous adjoint method and the finite element method.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13021号 / 論農博第2831号 / 新制||農||1042(附属図書館) / 学位論文||H28||N4967(農学部図書室) / 32949 / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 藤原 正幸, 教授 村上 章, 准教授 宇波 耕一 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Flooding has always been and is still today a disastrous event with agricultural, infrastructural, economical and not least humanitarian ramifications. Understanding the behaviour of floods is crucial to be able to prevent or mitigate future catastrophes, a task which can be accomplished by modelling the water flow. In this thesis the finite element method is employed to solve the shallow water equations, which govern water flow in shallow environments such as rivers, lakes and dams, a methodology that has been widely used for flooding simulations. Alternative approaches to model floods are however also briefly discussed. Since the finite element method suffers from numerical instabilities when solving nonlinear conservation laws, the shallow water equations are stabilised by introducing a high-order nonlinear artificial viscosity, constructed using a multi-mesh strategy. The accuracy, robustness and well-balancedness of the solution are examined through a variety of benchmark tests. Finally, the equations are extended to include a friction term, after which the effectiveness of the method in a real-life scenario is verified by a prolonged simulation of the Malpasset dam break.

Observations of Jupiter show a super-rotating (prograde) equatorial jet that has persisted for decades. Shallow water simulations run in the Jovian parameter regime reproduce the mixture of robust vortices and alternating zonal jets observed on Jupiter, but the equatorial jet is invariably sub-rotating (retrograde). Recent work has obtained super-rotating equatorial jets by extending the standard shallow water equations to relax the height field towards its mean value. This Newtonian cooling-like term is intended to model radiative cooling to space, but its addition breaks key conservation properties for mass and momentum. In this thesis the radiatively damped thermal shallow water equations are proposed as an alternative model for Jovian atmospheres. They extend standard shallow water theory by permitting horizontal variations of the thermodynamic properties of the fluid. The additional temperature equation allows a Newtonian cooling term to be included while conserving mass and momentum. Simulations reproduce equatorial jets in the correct directions for both Jupiter and Neptune (which sub-rotates). Quasi-geostrophic theory filters out rapidly moving inertia-gravity waves. A local quasi-geostrophic theory of the radiatively damped thermal shallow water equations is derived, and then extended to cover whole planets. Simulations of this global thermal quasi-geostrophic theory show the same transition, from sub- to super-rotating equatorial jets, seen in simulations of the original thermal shallow water model as the radiative time scale is decreased. Thus the mechanism responsible for setting the direction of the equatorial jet must exist within quasi-geostrophic theory. Such a mechanism is developed by calculating the competing effects of Newtonian cooling and Rayleigh friction upon the zonal mean zonal acceleration induced by equatorially trapped Rossby waves. These waves transport no momentum in the absence of dissipation. Dissipation by Newtonian cooling creates an eastward zonal mean zonal acceleration, consistent with the formation of super-rotating equatorial jets in simulations, while the corresponding acceleration is westward for dissipation by Rayleigh friction.

With the advances in the computing world, computational fluid dynamics (CFD) is becoming more and more critical tool in the field of fluid dynamics. In the past few decades, a huge number of CFD models have been developed with ever improved performance. In this research a robust CFD model, called Riemann2D, is extended to model flow over a mobile bed and applied to a full scale dam break problem. Riemann2D, an object oriented hyperbolic solver that solves shallow water equations with an unstructured triangular mesh and using high resolution shock capturing methods, provides a generic framework for the solution of hyperbolic problems. The object-oriented design of Riemann2D has the flexibility to apply the model to any type of hyperbolic problem with the addition of new information and inheriting the common components from the generic part of the model. In a part of this work, this feature of Riemann2D is exploited to enhance the model capabilities to compute flow over mobile beds. This is achieved by incorporating the two dimensional version of the one dimensional non-capacity model for erodible bed hydraulics by Cao et al. (2004). A few novel and simple algorithms are included, to track the wet/dry and dry/wet fronts over abruptly varying topography and stabilize the solution while using high resolution shock capturing methods. The negative depths computed from the surface gradient by the limiters are algebraically adjusted to ensure depth positivity. The friction term contribution in the source term, that creates unphysical values near the wet/dry fronts, are resolved by the introduction of a limiting value for the friction term. The model is validated using an extensive variety of tests both on fixed and mobile beds. The results are compared with the analytical, numerical and experimental results available in the literature. The model is also tested against the actual field data of 1957 Malpasset dam break. Finally, the model is applied to simulate dam break flow of Warsak Dam in Pakistan. Remotely sensed topographic data of Warsak dam is used to improve the accuracy of the solution. The study reveals from the thorough testing and application of the model that the simulated results are in close agreement with the available analytical, numerical and experimental results. The high resolution shock capturing methods give far better results than the traditional numerical schemes. It is also concluded that the object oriented CFD model is very easy to adapt and extend without changing the generic part of the model.

Flood inundation is a major natural hazard that can have very severe socio-economic consequences. This thesis presents an enhanced numerical model for flood simulation. After setting the context by examining recent large-scale flood events, a literature review is provided on shallow flow numerical models. A new version of the hyperbolic horizontal variable density shallow water equations with source terms in balanced form is used, designed for flows over complicated terrains, suitable for wetting and drying fronts and erodible bed problems. Bed morphodynamics are included in the model by solving a conservation of bed mass equation in conjunction with the variable density shallow water equations. The resulting numerical scheme is based on a Godunov-type finite volume HLLC approximate Riemann solver combined with MUSCL-Hancock time integration and a non-linear slope limiter and is shock-capturing. The model can simulate trans-critical, steep-fronted flows, connecting bodies of water at different elevations. The model is validated for constant density shallow flows using idealised benchmark tests, such as unidirectional and circular dam breaks, damped sloshing in a parabolic tank, dam break flow over a triangular obstacle, and dam break flow over three islands. The simulation results are in excellent agreement with available analytical solutions, alternative numerical predictions, and experimental data. The model is also validated for variable density shallow flows, and a parameter study is undertaken to examine the effects of different density ratios of two adjacent liquids and different hydraulic thrust ratios of species and liquid in mixed flows. The results confirm the ability of the model to simulate shallow water-sediment flows that are of horizontally variable density, while being intensely mixed in the vertical direction. Further validation is undertaken for certain erodible bed cases, including deposition and entrainment of dilute suspended sediment in a flat-bottomed tank with intense mixing, and the results compared against semi-analytical solutions derived by the author. To demonstrate the effectiveness of the model in simulating a complicated variable density shallow flow, the validated numerical model is used to simulate a partial dam-breach flow in an erodible channel. The calibrated model predictions are very similar to experimental data from tests carried out at Tsinghua University. It is believed that the present numerical solver could be useful at describing local horizontal density gradients in sediment laden and debris flows that characterise certain extreme flood events, where sediment deposition is important.

Title: Influence of buoyancy dumb-bells on load intensity during shallow water aerobic Objectives: The aim of this theses was to compare the heart rate to several variants during 14 minutes head-out aquatic exercise (with simultaneous legs and arms actions and with simultaneous legs and arms actions using buoyancy dumb-bells). 8 females, clinically healthy and with a regular level of physical activity in age between 25-60 years (age 42 ± 11,4 years) were studied. The other aim of this theses was to compare the heart rate during rest on land and rest in water during shallow water aerobic in an upright position with water level to shoulder depth. Methods: We monitored heart rate changes during 14 minutes head-out aquatic exercise by Sport Tester S610i. The results of the tests were analyzed and evaluated with Polar Precision Performance software. Chi-squared test was used to examine the average difference to heart rate during tests. Results: We found non-significant increases on load intensity during test with using buoyancy dumb-bells. Average heart rate during rest in water showed decreases by 13 beats per minute. Keywords: buoyancy dumb-bells, load intensity, heart rate, shallow water aerobic

In the present work we study the numerical solution of shallow water equations. We introduce a vectorial notation of equations laws of conservation from which we derive the shallow water equations (SWE). There is the simplify its derivation, notation and the most important features. The original contribution is to derive equations for shallow water without the using of Leibniz's formula. There we report the finite volume method with the numerical flow of Vijayasundaram type for SWE. We present a description of the linear reconstruction, quadratic reconstruction and ENO reconstruction and their using for increasing of order accuracy. We demonstrate using of linear reconstruction in finite volume method of second order accuracy. This method is programmed in Octave language and used for solving of two problems. We apply the method of the ADER type for the shallow water equations. This method was originally designed for the Euler's equation.