Pedro Manso

Influence of Plunge Pool Geometry on High-Velocity Jet Impact Pressures and Pressure Propagation inside Fissured Rock Media

The geometrical development of unlined plunge pools downstream large dams depends on both local geology and type of plunging jet and its diffusion pattern. Experimental investigations in plunge pools with different lateral confinements are presented. They show that the pool geometry influences plunging jet diffusion, air entrainment in the pool, and, as a consequence, impact pressures at the water-rock interface and inside the fissured rock mass. Results include impact pressures definition for variable pool depths, jet velocities, and pool geometries, depending explicitly on the lateral confinement of the jet. The main pool flow features are described focusing on their contribution to energy dissipation. Should the lateral confinement limit the development of macroturbulent rollers around the plunging jet (instead of the pool depth), the mean pressures at impact are considerably reduced, as well as RMS pressures in transitional and deep pools. For shallow pools, RMS pressures increase as a result of enhanced jet development.

Opportunity and Economic Feasibility of Inline Microhydropower Units in Water Supply Networks

AbstractSmall-scale hydropower is emerging as a decentralized source to satisfy local demand for electricity. In water supply systems, microhydropower can be used for energy recovery associated with excessive pressure control. However, there is a lack of specific solutions for applications within networks where discharges are highly variable and there are limitations of pressure. An arrangement of microturbines specially conceived for water supply networks is proposed, based on a recently tested microturbine for inline installation in pipes. The installation of up to four turbine units is possible within a buried chamber created around an existing pipe. The location of the chambers is analyzed using an optimization algorithm that considers two objective functions: energy production and economic value. The feasibility of the proposed arrangement for a microhydropower plant was assessed through a case study of a subgrid of the water supply network of Lausanne, Switzerland. A detailed analysis of the cost br...

Design of Pressure Relief Valves for Protection of Steel-Lined Pressure Shafts and Tunnels Against Buckling During Emptying

Using high-strength steels for pressure shafts and tunnel liners and taking into account significant rock mass participation allows the design of comparatively thin steel liners in hydropower projects. Nevertheless, during emptying of waterways, these steel linings may be endangered by buckling. Compared with traditional measures such as increased steel liner thickness and stiffeners, pressure relief valves are a very economical solution for protection of steel liners against critical external pressure and therefore buckling during emptying. A calculation procedure has been developed for the design of the required number and arrangement of pressure relief valves, and this has been used successfully in practice. Systematic model tests enabled the assumptions of the design method to be verified.

Fluid–structure interaction in pipe coils during hydraulic transients

ABSTRACT The paper presents the analysis of fluid–structure interaction occurring during hydraulic transients in pipe coils by means of a four-equation model. The purpose is to understand and describe the effect of the coil movement on the transient wave. The four-equation model couples the transient pipe flow with the axial movement of the pipe-wall neglecting radial inertia, flexure and torsion of the piping system. Three models have been developed: the first simplifying the coil to a straight pipe with a moving valve, the second model assuming independent axial deformation in each coil ring, and the third model that includes dry friction dissipation. The first allows an easier generalization of the method; however, it does not allow the complete description of the phenomenon; the second and third models fit better the experimental observations in the pipe coil facility, suggesting that its behaviour is dominated by the independent movement of the rings.

Fluid-Structure Interaction Models in Pressurized Fluid-Filled Pipes: A Review

The present review paper aims at collecting and discussing the research work, numerical and experimental, carried out in the field of Fluid-Structure Interaction (FSI) in one-dimensional (1D) pressurized transient flow in the time-domain approach. Background theory and basic definitions are provided for the proper understanding of the assessed literature. A novel frame of reference is proposed for the classification of FSI models based on pipe degrees-offreedom. Numerical research is organized according to this classification, while an extensive review on experimental research is presented by institution. Engineering applications of FSI models are described and historical accidents and post-accident analyses documented.

Impacts du changement climatique sur la production hydroélectrique alpine : comment une nouvelle retenue à Oberaletsch pourrait garantir la gestion durable des installations existantes

Suite à décision du Conseil Fédéral de sortir du nucléaire, l’hydroélectricité suisse jouera un rôle central pour réussir la transition énergétique. Cependant, le changement climatique semble avoir un impact négatif sur la production hydraulique à long terme. En effet, avec l’accélération de la fonte des glaciers, les apports hydrauliques vont en général augmenter jusqu’en 2050, puis diminuer avec la disparition d’un grand nombre de glaciers. Ce phénomène va laisser place à des sols très érodibles, les moraines, ce qui se traduira par une augmentation globale de l’apport en sédiments aux retenues existantes. La diminution globale des apports en eau va donc impacter la gestion des barrages, comme celui de Gebidem, dans le canton du Valais en Suisse, déjà très concerné par la gestion des sédiments. Ce barrage est situé en aval du grand glacier d’Aletsch et exploite les eaux de la Massa à la centrale de Bitsch. Le volume de la retenue ne représentant que 2% de l’ensemble des apports de son bassin versant. Le retrait du glacier, et notamment de son bras d’Oberaletsch laisse apparaître un site idéal pour l’implantation d’une nouvelle retenue en amont de Gebidem, ce qui permettrait d’une part d’exploiter une nouvelle hauteur de chute et d’autre part de pouvoir augmenter la capacité de stockage saisonnier permettant une meilleure valorisation de la ressource en eau et une plus grande flexibilité d’exploitation. L’article présente une étude du potentiel du site d’Oberaletsch focalisé sur la possibilité de convertir les futurs impacts du changement climatique en opportunités. La construction d’un nouvel aménagement à Oberaletsch à caractère modulable permettrait de capter l’abondance des apports dans les prochaines décennies et de se préparer pour leur réduction attendue après 2050. Les effets combinés d’une nouvelle retenue et d’un moindre transit des apports en eau en rivière, réduiraient la mobilisation des dépôts de moraine et les apports en sédiments à Gebidem. Une exploitation coordonnée des deux aménagements permettrait des gains d’efficience dans l’usage de l’ensemble des ressources en eau, du territoire et des infrastructures, toute en réduisant et modulant les investissements en nouvelles installations.