A 1-D tidal, salinity and water quality model that analyzes the general effects freshwater diversions have on the water quality of the Pontchartrain Estuary over a 17-year period is presented here. Using the modeled live algae concentrations in conjunction with the algal bloom probability model results produces an accurate prediction of algal bloom occurrences between 1990 and 2006. The model predicts that the addition of freshwater diversions into Maurepas swamp and increases to flow in the Bonnet Carré Spillway may cause more intense and frequent algal blooms to occur around the Pontchartrain Estuary. The model also predicts that high nutrient input events that occur earlier in the year (January/February) will not likely have algal blooms associated with them. When nutrient input events (even small events) occur in the late spring or early summer, algal blooms have a high probability of occurring when the salinity, temperature and light levels are sufficient.

This dissertation presents a study on the development of a numerical model aimed at simulating free surface flow, which still remains an active research area. Modeling these processes is very challenging since the interface between air and water is characterized by sharp discontinuities in fluid properties and flow characteristics due to different densities, viscosities, surface tension and consequent discontinuities in spatial gradients of velocity and pressure. The constraint of incompressibility poses another difficulty on the efficient design of algorithms. Recently, the level set method has emerged as a powerful tool for evolving interfaces in computational science and engineering for a wide range of applications while the finite element method has been long known for its geometrical flexibility. An effort to combine these two methods is made in this study. Several benchmark problems are used for the test of the developed code in view of temporal and spatial accuracy. Then, the capability and efficiency of the model are extended with advanced turbulence models and parallel algorithm. The model is applied to problems of practical importance in hydraulics, including hydraulic jump under a sluice gate and the design of spillways for fish migration. The main focus is on the capturing of free surface and identifying and understanding of the vortical structures and nonhydrostatic pressure distribution. The model has proved to be very effective for these purpose. The new technique dealing with air-water interface in a more physically accurate way is introduced for future development and the new method is applied to the problems of static equilibrium for validation.

Today’s climate changes will probably give rise to precipitation in Sweden, which will cause more floods in Swedish rivers. Many of the Swedish rivers are regulated and have lots of hydro-electro power plants. Higher floods in the rivers will give greater water loads on the dams, which mean that a higher discharge through the sluice gates and in the spillway channels is needed. High discharge of water in a spillway channel can create scour of the material in the channel. Usually, for spillways in Swedish hydropower plants, this material is rock and the scour is in form of rock blocks. Scour downstream of dams can in the worst case endanger the dam construction. The purpose of this study was to identify the extent and the type of rock scour that may appear in spillway channels of Swedish hydro power plants. The scour in rock material in a spillway channel is usually caused by pressure fluctuations in the water, which can cause large differences in pressure on the top and bottom surfaces of blocks. This pressure difference can be high enough to lift whole blocks. The main factors that affect this kind of scour are the crack pattern of the rock mass, the geometry of the spillway, the discharge of water and the surface fluctuation in the water. In this study a numeric model analyse, a field study and a literature study has been made in order to examine the influence on scour of the orientation of cracks in a rock mass. A rock mass containing a group of cracks with small or no dip is more likely to scour when it is exposed to discharging water. The orientation of the cracks in a rock mass relative to the direction of the water flow has also an impact on the capacity of the rock mass to resist scour. In the field study the scour pattern in the spillway channels of the hydro power plants in Ligga, Harsprånget, Porjus, Satisjaure and Seitevare was examined. The scour of rock mass in the spillway channels in Ligga, Harsprånget and Porjus has been extensive. The rock mass in these channels has bedding cracks of small distances. This is probably the reason why these rock masses are sensitive for loads from discharging water. The rock mass in the spillway channel in Satisjaure has lots of cracks and is also very sensitive for loads from discharging water. This channel has been rebuilt during 2004. There are different methods to predict the ability of a rock mass to resist scour. The Erodibility Index Method is a semi-empirical method that is verified by field observations in the USA. In this work the ability to apply this method on Swedish channels has been examined with field observations from Porjus, Harsprånget and Seitevare. As the Erodibility Index Method seemed to work in the case of these three spillways, it was also applied on the spillways in Satisjaure and Ligga. Measures to reduce the energy in the discharging water in the spillways are very effective to reduce the risk of scouring in the rock mass. Blasted stairs in the rock mass in a channel or a stilling basin downstream the sluice gate is something that can reduce the energy in discharging water. Further documentary of spillway channels, like mapping and laser scanning, would contribute to a further verification of the Erodibility Index Method and to get a general survey of the risk of scour in Swedish spillways. / Dagens klimatsituation ser ut att ge ökad mängd nederbörd i Sverige, vilket innebär att de svenska älvarna kommer att utsättas för allt högre vattenflöden. De flesta av Sveriges älvar är reglerade, d v s längs älvarna finns en mängd större och mindre dammar. Ett högre flöde i älvarna innebär även rikligare tillrinning till dammarna vilket medför att avbördningen från dem måste bli större. Avbördningen från dammarna sker genom utskov och höga vattenflöden i utskovskanalerna kan orsaka erosion på det berg som kanalen vanligen består av. Erosionen är av typen ”blockerosion” där hela bergblock av större eller mindre storlek lösgörs från bergmassan. I värsta fall kan blockerosionen krypa uppströms och erodera dammkroppen bakifrån, vilket skulle kunna innebära att dammen brister. Syftet med detta arbete var att identifiera omfattning och typ av bergerosionsproblem som uppkommer i utskovskanaler. Blockerosion uppkommer i regel då forsande vatten skapar tryckskillnader mellan övre och undre ytan på block. Tryckskillnaden kan då skapa tillräckliga lyftkrafter för att block ska lossna. De huvudsakliga faktorerna som styr blockerosionen är bergmassans sprickighet och material, utskovskanalens geometri och vattnets flöde och ytfluktuation. Genom litteraturstudie, numerisk modellanalys samt fältstudie har inverkan på blockerosionen av sprickriktningar utretts. En bergmassa som innehåller sprickgrupper som har liten, nära horisontell, stupning är känslig för vattenbelastning. Stupningsriktningen i förhållande till flödesriktningen har också betydelse för blockerosionen. Stupningsriktning i flödesriktningen gör bergmassan mer känslig för belastning av forsande vatten och gynnar därmed erosionen. Utskovskanalerna i Ligga, Harsprånget, Porjus, Satisjaure samt Seitevare har undersökts med avseende på erosionsrisk. Erosionen i Ligga, Harsprånget och Porjus har varit omfattande och detta beror troligtvis på att dessa kanaler har subhorisontella bankningssprickor med litet sprickavstånd. I Satisjaure är bergmassan mycket sprickig, varför denna kanal är mycket känslig för vattnets belastning. Där har dock åtgärder vidtagits så att kanalen ska tåla sitt dimensionerande flöde. I Seitevare är erosionsrisken i kanalens övre del liten. Det finns olika metoder för att bedöma erosionsrisken i en bergmassa. Erosionsindexmetoden är en semiempirisk metod som är verifierad med platsobservationer i USA. Med hjälp av observationer från Porjus, Harsprånget och Seitevare har erosionsindexmetodens tillämplighet på svenska kanaler undersökts. För dessa tre observationer verkar metoden fungera bra och har därför även använts i kanalerna i Satisjaure och Ligga. Energidämpande åtgärder i kanalerna, såsom energiomvandlargropar och utsprängda trappor i kanalerna, har visats sig vara mycket effektivt för att minska erosionsrisken. En noga dokumentering av utskovskanaler, som t ex kartering och inmätningar, skulle bidra till att erosionsindexmetoden kunde verifieras ytterligare och att en översiktlig bedömning av erosionsrisken i utskovskanaler enkelt kan erhållas.

Dauguma hidrotechnikos statinių naudojami daugiau negu 30 metų. Praktiškai kiekviename statinyje yra gelžbetoninių konstrukcijų. Gelžbetonis yra patvari medžiaga, tačiau ilgainiui dėl įvairių priežasčių (natūralus medžiagų senėjimas, įvairios apkrovos ir veiksniai: mechaniniai, fiziniai, cheminiai, specifiniai), konstrukcijose, pagamintose iš šios medžiagos, atsiranda pokyčių bloginančių statinio naudojimo savybes, trumpinančių gyvavimo trukmę. Betono ir gelžbetonio irimo procesai labai sudėtingi, nes kartu veikia daug įvairių veiksnių, keičiančių fizines ir mechanines savybes. Todėl konstrukcijų patvarumas priklauso nuo šių irimo procesų intensyvumo. Konstrukcijų patvarumo esminiai reikalavimai pateikiami statybos reglamente STR 1.12.05:2010. Tyrimo tikslas – ištirti, įvertinti ir palyginti Marijampolės, Šakių, Vilkaviškio, Kėdainių rajonų slenkstinių pralaidų būklę su ankstesnių tyrimų rezultatais. Mokslinių ekspedicijų metu 2011 – 2012 m. vizualiai buvo ištirtos dešimties slenkstinių pralaidų būklė, jų amžius yra 50 – 60 metų, seniausia 76 metai. Tiriant slenkstinių pralaidų pažaidų būklės kitimą buvo naudoti šie konstrukcijų diagnostikos metodai: kameraliniai darbai; vizualinis metodas; neardantis metodas betono stipriui nustatyti (instrumentinis); slenkstinių pralaidų techninė būklė įvertinta balais pagal STR.1.12.03:2006 pateiktą metodiką; statistiškai apdoroti duomenys „MS EXCEL“ kompiuterine programa. Palyginus 2011 – 2012 m. tyrimų su ankstesnių (1999 – 2009 m... [toliau žr. visą tekstą] / Most hydraulic structures are used by more than 30 years. Practically every building is of reinforced concrete structures. Reinforced concrete is a durable material, but eventually for various reasons (natural aging of materials, loading and various factors: the mechanical, physical, chemical, specific) changes occur in the structures made of these materials worsening usage properties of the structure, shortening the life span. Concrete and reinforced concrete degradation processes are very complicated because a variety of factors that change the physical and mechanical properties operate at the same time. Therefore, the durability of structures depends on the intensity of decomposition processes. Essential requirements of structural stability are presented in the construction regulation STR 1.12.05:2010. The aim of the research was to investigate, evaluate and compare condition of overflow spillways situated in Marijampolė, Šakiai, Vilkaviškis and Kėdainiai districts with previous results. During scientific expeditions in 2011 – 2012 the condition of ten overflow spillways were examined visually, their age is 50 – 60 years old, the oldest is 76 years old. Studying condition changes of the damages in overflow spillways the following structure diagnostic methods were used: Indoor works; Visual method; Non-destructive method for the determination of the strength of concrete (instrumental); The technical condition of overflow spillways was evaluated by scoring... [to full text]

Mit dem Begriff "Schachtüberfall" wird eine Hochwasserentlastungsanlage bezeichnet, bei der Überschußwasser von einem horizontalen, im Grundriß meist kreisförmigen Überfall in einen senkrechten oder schrägen Schacht geleitet und durch einen Stollen mit geringem Gefälle ins Unterwasser abgeführt wird. Der Fallschacht hat in der Regel Kreisquerschnitt und ist durch einen 90°-Krümmer mit dem Ablaufstollen verbunden. Schachtüberfälle werden in zunehmenden Maße zur Hochwasserentlastung bei Erd- und Steindämmen verwendet. Sie werden getrennt vom Dammbauwerk im Hang oder als freistehende Türme im Becken errichtet. (...)

Orientador: Ana Ines Borri Genovez / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-09T18:19:12Z (GMT). No. of bitstreams: 1 Ferreira_LauraMariaCanno_D.pdf: 6902999 bytes, checksum: 3e1f02a65f335b50df38d55fa7ab47bd (MD5) Previous issue date: 2007 / Resumo: Estruturas de queda com poços verticais podem ser utilizadas para drenagem urbana, dissipação de energia e como vertedores em barragens. No último caso, tem-se os vertedores com emboque tipo tulipa, formados por um perfil vertedor seguido de um poço vertical, que se liga a um túnel por meio de uma curva. A curva é um ponto crítico do dimensionamento do vertedor, pois, é onde o escoamento o deflete, causando elevadas pressões na sua parte convexa e subpressões na parte côncava. Este trabalho tem, como objetivo, o estudo experimental de um vertedor tipo tulipa, para definir uma melhor geometria para a curva de ligação poço-túnel. Um estudo experimental foi feito, empregando-se o modelo do vertedor de Paraitinga, em escala 1:51,02, utilizando novas geometrias para a curva, para avaliar as pressões e o arraste de ar. Pôde constatar-se a nfluência da geometria da curva, sendo que as novas curvas resultaram em um escoamento mais regular, acompanhando o traçado da curva, com pressões menores na parte convexa, além de uma maior vazão de afogamento do vertedor. Foram propostas equações para o cálculo da vazão de ar em função da concentração média do ar no escoamento. Através do estudo experimental comparativo entre as diferentes curvas se sugere o emprego da curva clotóide para ser usada na ligaçao poço-túnel / Abstract: Vertical dropshafts can be used in drainage systems, energy dissipator and as dam spillways. In this case, they are called morning glory, and consists of an inlet followed by a shaft which joins a tunnel through a bend. The bend is a critical point in spillway sizing, therefore the flow deflects in this region and causes high pressures in the convex part of the bend and negative pressures in the concavous part. This paper cares for the experimental study to define a better geometry for the shaft spillway vertical bend. An experimental study has been carried out, using the spillway model of Paraitinga dam, which scale was 1:51,02, using new bend geometries, to evaluate pressures flow and air entrainment. The influence of the bend geometry has been noticed, and the new curves resulted in a more regular flow, that followed the trace of the curve, with smaller pressures in the convex part, besides a higher flow to submerge the spillway. Equations have been proposed to calculate air entrainment flow as a function of the average concentration of air. Through the experimental study to compare the different curves, one suggest the use of use clotóide curve, as a bend shaft / Doutorado / Recursos Hidricos / Doutor em Engenharia Civil

This thesis deals with mathematical modelling of water flow through the safety object. It explains the principle of mathematical modelling and its laws. There is also present-ed the mathematical models used by numerical modelling. The results of mathemati-cal model Koryčany are included in this thesis compared with hydraulic calculations and physical model.

The master´s thesis deals with the numerical modeling of flow in the emergency spillways of small dams. It is solved the flow rate capacity of a weir and of spillway called „duckbill-type“. Sharp crested weirs and long crested weirs are modeled using numerical simulations in ANSYS. Hydraulically complex spillway called „duckbill-type“ was modeled in the Flow-3D. The results of the discharge coefficients are compared with data in the hydraulic literature.

Major cavitation damages can seriously endanger the stability of hydraulic structures, in worst case lead to dam failure. To remedy the effect of cavitation on spillway chutes the most common method today is aeration of the flow. Aerators introduce air to the bottom layers of the flow, enough to prevent damages to occur in the concrete lining. The design of an aerator system is of a complex manner due to the many involving parameters such as the channel slope, ramp angle, Froude number, flow velocity. In this report the susceptibility of the Höljes Dam to cavitate has been outlined with the result that this would occur at an extreme and most unlikely situation and remedial measures have been proposed. The design of an aerator system has been proposed as the result from theoretical research. A physical hydraulic model to assess the efficiency of a proposed aerator design is highly recommended. Alternative causes to the damages observed in the spillway chute are discussed.

The main aim of this Master Thesis is the design of several hydraulic structures to decrease as much as possible the huge flooding caused by the Escartana gully which drains its water towards the city of Albacete (Spain) and its surrounding areas, affecting to their inhabitants; and causing huge material damages in residential and industrial areas, and loss of crops in nearby farmland. Some alternatives such as embankment dams with or without drainage systems inside the dam body and a roller-compacted concrete (RCC) dam have been proposed to be built, being necessary to carry out a multicriteria analysis in order to decide which alternative has the best fit according to the analyzed features of the region. The alternative chosen to be developed was the RCC dam for the advantages of this typology, currently in development and implantation in some countries like Spain. For this reason, a RCC dam is planned to be built some kilometers upstream of these areas, with the objective of controlling the future floods coming from this watershed by decreasing its peak flow. In order to increase the beneficial effects of the construction of the dam, a channel downstream is also designed to drain the discharged overflows by the drainage systems of the dam towards a natural endorheic area, the Salobral Lagoon (currently dried-up), located 13 kilometers downstream of the dam’s location. This lagoon is connected hydraulically to the drainage network of Albacete by means of the Salobral channel and due to its huge storage capacity, it allows to reduce substantially the peak flows over the Salobral channel avoiding the dangerous flooding and potential damages caused by them. As a result of the projected hydraulic structures, Albacete and its surrounding areas would increase substantially their protection against the floods coming from the Escartana watershed.