A soleira lateral desempenha um papel importante nos reservatórios de detenção/ retenção (off-line), atuando na captação das vazões afluentes e evitando possíveis enchentes, problema em destaque nos períodos chuvosos das principais capitais brasileiras. Um melhor entendimento do seu comportamento hidráulico possibilitará o desenvolvimento de estruturas laterais mais eficientes. O presente trabalho tem como objetivo criar um modelo da soleira lateral através da tecnologia CFD (Dinâmica dos Fluidos Computacional) e validá-lo através de experimentos em modelo reduzido do Laboratório de Hidráulica da Escola Politécnica da USP. A partir disso, explorar as características hidráulicas do modelo de CFD, como o comportamento dos níveis dágua e a distribuição de velocidades. No estudo da validação estudaram-se três tipos de refinamento de malhas e três modelos de turbulência (k-, k- (RNG) e SST k-). O modelo computacional validado é composto pela malha 3, com um refinamento cerca de 342000 elementos (hexaédricos predominante), e o modelo de turbulência k- (RNG), que apresentaram a maior precisão dos resultados. A análise da distribuição de velocidades possibilitou visualizar uma região de mínima velocidade abaixo da soleira lateral, e também quantificar uma região de baixas velocidades no início da soleira, onde é pequena a eficiência das vazões escoadas. Através do comportamento da superfície dágua foi possível visualizar a região de influência do dispositivo lateral no canal principal. A comparação do coeficiente de descarga do modelo de CFD com trabalhos de outros pesquisadores, um nacional e outro internacional, mostrou a representatividade do modelo criado para condições diferentes. A ferramenta CFD é promissora para o estudo de estruturas hidráulicas, contribuindo para o seu desenvolvimento e aperfeiçoamento. / The side weir plays an important role in the detention / retention tanks (off-line), operating in the uptake of water inflow and preventing possible flooding, which is a highlighted problem on rainy periods of the main Brazilian capitals. A better understanding of the hydraulic behavior allows the development of more efficient lateral structures. This work aims at creating a model of the side weir through CFD technology (Computational Fluid Dynamics) and validating it through experiments on a reduced model of the Laboratório de Hidráulica da Escola Politécnica da USP. Thereafter, explore the hydraulic characteristics of the CFD model, like the behavior of water levels and the velocity distribution. In the validation study, three types of mesh refinement and three turbulence models were studied (k-, k- (RNG) and SST k-). The computational model is validated by the composite mesh 3 with a refinement about 342,000 elements (hexahedral predominant), and the turbulence model k- (RNG), which had the highest precision of results. Analysis of the velocities distribution allowed us to visualize a region of minimum velocity below the side weir, and also to quantify a region of low velocities at the beginning of the weir, where the efficiency of overflows is small. Through water surface behavior it was possible to visualize the influence region of the side device in the main channel. A comparison of discharge coefficient of the CFD model between other works (one national and the other one international) showed the representativeness of the model created for different conditions. The CFD is a promising tool for the study of hydraulic structures, contributing to its development and improvement.

In recent years, magnitudes of flood estimates used in hydraulic design have increased for many reservoirs. Consequently, many existing spillways are now deficient as they do not meet current discharge capacity requirements. To rehabilitate existing, fixed-width spillways, labyrinth weirs are often viable solutions. For reservoir applications, arcing labyrinth weirs into the reservoir increases hydraulic efficiency. This results from better cycle orientation to the approaching flow field. This study supplements available arced labyrinth weir hydraulic data by observing flow characteristics of three laboratory-scale physical models and two numerical (CFD) models. Physical model results provide head (energy)-discharge data and empirical coefficients for hydraulic design. Results also show that increasing the arc angle improves efficiency at H/P<0.3, where H/P is upstream piezometric head divided by weir height; after which, efficiency improvements diminish as downstream submergence also increases. The purpose of the CFD analysis was to assess the appropriateness of CFD as a design tool for arced labyrinth weir head-discharge relationship development. The CFD model results found good agreement with the physical model data indicating CFD’s usefulness as a hydraulic design tool; however, it is recommended that CFD models be calibrated to reliable laboratory or field data. This study’s data may be used, with sound engineering judgement, to aid in hydraulic design of arced labyrinth weirs

The rehabilitation of dams often requires spillway capacity upgrades. Replacing a less hydraulically efficient linear weir with a labyrinth weir can be an effective way to increase discharge efficiency (discharge at a given upstream head) for a fixed-width channel. Labyrinth weirs are linear weirs folded in plan view to increase total spillway crest length (which in turn increases discharge efficiency within a channel). Labyrinth weirs potentially have limitless geometric configurations. This study was performed to analyze the effects of varying certain geometric parameters on discharge efficiency and design method predictions. Due to limited cross-sectional flow area near the upstream apex, labyrinth weirs experience nappe collision and local submergence that potentially reduce discharge efficiency. The increase of upstream apex width may be a feasible method to decrease the negative effects of nappe interference, which in turn may increase discharge efficiency. This was analyzed in this study by testing a series of eight laboratory scaled labyrinth weirs (with sidewall angles of 12°), with various upstream apex widths. Upstream apex width tests were performed in a fixed and varied channel width setting. The design method developed by Crookston and Tullis is based on laboratory scaled physical models. This method is very useful in the estimation of performance for geometrically similar prototype labyrinth weirs. However, due to difficulty in obtaining data on completed prototype weirs, design method predictions are rarely verified. To help validate Froude scaling and design method predictions of prototype weirs, a series of physical model tests (with sidewall angles of 15°) were performed with varying scale sizes (0.5 to 3.0 compared to the size of weir used in the design method). To expand the applicability of the design method to common geometric variations, tests were performed on weirs of varying weir height and cycle width (with sidewall angles of 15°). These variations were applied independently and analyzed to determine their effects on discharge efficiency and design method predictions. A correction factor is then presented to be used in conjunction with Crookston and Tullis’s design method for these geometric variations. All conclusions are presented in this thesis.

Linear weirs are a common hydraulic structure that have been used for centuries with many different applications. One characteristic of weirs that is particularly useful is the head-discharge relationship where the discharge over the weir is directly related to the upstream water depth above the crest. In general, the head-discharge relationship for a weir is determined experimentally in laboratories using geometrically similar models. Due to space, time, money, and discharge capacity limitations at water laboratories, creating full scale models is not always a feasible option when determining head-discharge relationships for large prototype weirs. It is typically more cost effective to create a scale model than to build a full scale model or conduct tests on the prototype. Because of this fact, physical modeling has been one the most important tools in determining head-discharge relationships for weirs. However, as the physical size of the model decreases, size scale effects associated with surface tension and viscosity forces can significantly affect the results from the physical model and cause the results to differ from what would actually occur at the prototype scale. Therefore, it is important to understand what affects surface tension and viscosity forces have on the head-discharge relationship for different size weirs and when those effects are no longer negligible. The purpose of this research was to evaluate size scale effects for linear weirs. Weirs models of three different crest shapes (flat-top, quarter-round, and half-round) were constructed and tested at four different geometrically similar sizes [weir heights (P) = 24-, 12-, 6-, and 3-in]. This was done in order to evaluate how size scale effects affect the head-discharge relationship as model size decreases for different crest shapes. Discharge coefficients were calculated for relative upstream head values ranging from 0.01 ≤ Ht/P ≤ 2.0 for vented and non-vented conditions. Nappe aeration behavior was documented and compared to determine where differences in the nappe trajectory occurred as a result of scale effects. Comparisons were made with data from others researchers to determine if the recommendations for minimum head limits were similar to the results from this study. This study examined the errors in the discharge coefficient associated with size scale effects and suggested limits to avoidance depending on model scale and crest shape.

This study employed a GIS-based use-analysis on a network of recently mapped pre-Columbian earthworks lying on the west side of a Bolivian floodplain. This wetland region, called Llanos de Mojos, is home to many different types of artificial mounds that served different roles for the ancient communities who constructed them thousands of years ago. This new set of features, which was mapped by volunteers of the Proyecto Sistemas Informaticas Geograficas y Arqueologicas del Beni (ProSIGAB) was purported to be a network of fish weirs, linear earthworks built in rivers or floodplains that are designed to trap fish by exploiting seasonal floodwaters. This identification was based on their similarities with the Baures Hydraulic Complex on the east side of Mojos (Erickson 2000; McKey et al. 2016; Blatrix et al. 2018). Classification procedures made use of the features' physical attributes and relationships with other landscape features to identify them not just as fish weirs, but multi-use structures that connected infrastructure, impounded water, and trapped fish. When understood together with nearby forest island settlements, neighborhoods of agricultural fields, and drainage features, it is argued these earthworks played a substantial role in the lives of past inhabitants, demonstrating their ingenuity by fulfilling multiple functions in a complex anthropogenic landscape.

Low grade rip rap weirs installed in agricultural surface drainage ditches manage downstream eutrophication by slowing water flow, allowing sediments time to settle out of the water column and phosphorus (P) to sorb to soil. A laboratory experiment was conducted in microcosm chambers to simulate increased hydraulic residence time caused by weirs and two field studies were conducted to compare experimental data with field data and determine sediment deposition rates. One field study monitored weirs monthly after installation and the other measured weirs of varying ages. Weirs retained significantly more water and sediment than controls. Longer inundation times led to abiotic factors known to release P during hydrologic flux, but did not translate to reduced P storage. By converting intermittently inundated sediments into more consistently saturated sediments, weirs function as a viable conservation practice for about a year until temporary P retention mechanisms and sediment retention capacities are reached.

Reservoir releases for power generation often cause rapidly fluctuating water levels and increased velocities in certain downstream sections of rivers. These conditions and the natural geometry of the river can render certain sections of the river dangerous for recreation. Although public utilities take precautionary safety measures immediately downstream of the dam, their measures further downstream have been limited, if not non-existent. The placement of weirs between the dam and dangerous sections would retard the flow—slowing the rise in water levels and decreasing velocities at predetermined dangerous sections. Big Falls, on the New River near McCoy, Virginia, is a popular recreation spot and becomes dangerous at certain times of the day due to releases from Claytor Lake Dam. Several people have drowned at this location over the years. In this study, the influence of weirs placed upstream of Big Falls on the rise of water level and increase in velocity is investigated by an implicit finite difference computer model of one-dimensional gradually varied unsteady flow. The model allows for investigation of different weir geometries and placements, and the effectiveness of these weirs when subjected to various boundary conditions which arise from variations of the maximum peak release hydrograph from Claytor Lake Dam from May to September of 1983 and 1984. Results of the study consist of the optimum weir geometry and placement on the New River upstream of Big Falls. Criteria for determining the weir included physical location limitations, and the effectiveness of the weir in reducing the rate-of-rise of water levels and increased velocities at Big Falls. / M.S.

Dissertation (PhD)--Stellenbosch University, 1996. / One copy microfiche. / Some digitised pages may appear illegible due to the condition of the original microfiche. / ENGLISH ABSTRACT: The present network of now gauging stations in South Africa has grown from isolated observations on an ad extensive is to an extensive network of stations across the country. Standardised gauging stations to suit local conditions have been developed which include purposely desigll4:d compound weirs. Nearly all. compound gauging weirs In South Africa have. for practical reasons. been constructed without dividing walls. thus deviating lr',:.n the standards set by the British Standards Institution (1981). Uncertainty about the accuracy of calibration of such structures had to be darifi,ed and. where ~cessary. adjustments had to be made to existing calibration formulae in order to compensate for the de,,·iations. It was also necessary to determine whether the accuracies that could be attained were adequate in terms of the potential financial implications of inaccuracies. It has thus become necessary to re-evaluate the calibration of these structures which consist of mainly compound Crump .md sharp-crested weirs. Selected flow l"t'Cords were analysed and the data wa.\ used to determine the impact of errors on the required capacities of reservoirs. This wa., done in an anempt to provide guidelines for the accuracy required in flow records. An31ysing a single application of a flow record cannot provide guidelines for the required accuracy of a flow record and thus the gauging of flow. Although no general conclusions can be drawn. it appears thal the benefits arising from an improvement in the accuracy of a flow record are proportionally greater than the percentage improvement in accuracy. Three-dimensional flow conditions exist either upstream or downstream of the point of stage measurement depending on the presence or absence of diViding walls at a compound gauging weir. The existing calibro1tion theory does not account for the influences of three-dimensional flow conditions and a.-'isociatcd energy losses in the determination of the upstream total energy head. Hydraulic model tests were thus undenaken to detemline the magnitude of the resulting energy losses. New techniques were developed to compensate for these energy losses in the calibration theory of compound gauging weirs. Application of the new calculation techniques to rate compound weirs using a single point of stage measurement results in improvements in accuracy. It was found that compound weirs without dividing walls can be rated to greater levels of accuracy than weirs with dividing walls, where stage measurements are taken at a single point / AFRIKAANSE OPSOMMING: Die huidige nc!werk van vloclmectpumc III SUld-Afnka hel gegroei van gc'isoleerde waamemings op 'n ad hoc basis, tot 'n uitgebrcldc nctwerk. van meetpunte vcrsprei oor die hele land, Standaard mcetstruktuure aangepas vir plaaslike omstandighede is ontwikkei en sluit in doelgeboudc saamgestelde mcetstrukture. Byltans aile saamgestelde mcetstruklure in Suid-Afrika is weens praktisc oorwegings opgerig sonder verdeelmure, wal afwyk van die standaarde gestel deur die British Standards Institution (1981). Onsekerhede aangaande die akkuraathcid ,'an die kaJibrasie van sulke slrukture moes opgekJaar word en unpassjngs un die beSlaande leorie moes gedoen word om hier'OOf te kompenseer. iodien nodig. Oil was ook nodig om va~ Ie s,tel of akkuraathede Waf hulbaar is voldoende is, met inagneming Vlll poIensi~1c finamiitle implikasies van onakkuruthede. Oit hel dus nodig gcword om die bestaandc kaJibra.liic van saamgestelde meetstrukture. hoofsaakJik Crump en sterpkroin meetwaJle, Ie hcr·cval~r. Seleere vloei:rekords is ontl~ en die data is gcbruik om die impak van foule ~ bepaal op die berekende k.apasitei~ van opgaardamme. Oil IS gedoen in 'n poging om riglyne neer te Ie rakende die akkuraatheid verlang in 'n vloeirekord. Die ontleding van '0 enkele loepassing van 'n vloeirekord lewer nie genoegsame data om riglyne vas Ie stell. "ir die verlanp akkuraalheid van 'n vloeirekord of vloeimeling nie. AlhoeweJ geen duidelike riglyne hieruii vOilr1spruit nie. kom dit voor asof die voordele verkry uit '0 verbetering io die akkuraatheid van 'n vloeirekord in verhouding groter is as die vcrmiodering in die vloeimetingsfout. Drie-dimensionele II'loeitoeslande bestaan of stroomop of stroomaf van die punt van watervlakmeting, afl1iangende van die 'cenwoordigheid of afwesigheid van vcrdeelmure by 'n saamgestclde meetstlruktuur. Die beslaande kalibrasieleorie maak nie voorsiening vIr die invloed van drie-dimensionele vloeitoestande en die gepaardgaande energieverlicse op die bepahng van die totale stroomop energiehoogte nie. Hidrouliese mode1tor: sc is ondemeem om die omvang van die resulterende energieverliese vas te ste!. Nuwe tegnieke in die kaJibrasieteorie vir saamgestelde strukture is ontwikk.e1 0:t1 tc kompenseer vir hierdie energieverliese. 'n Verbc:tcde akkuraatheid word verkry wanneer die nuwe tegniek toegepas word op die kalibrasie van saamge~telde meetstrukture met 'n enkele punt van watervla.kmeting. Daar is gevind daR saamgestelde meetstrukture sonder verdeelmure illurater gekalibn:er lean word. as suuktt.Rmet vcrdeelmure waar walervlakke slegs by 'n enkclc punt gemeet word.

Tyrolean type water-intake structures are widely used on mountain rivers to provide water to hydropower stations. The main concern encountered in these kinds of structures is the amount of water diverted from the main channel and sediment carried by this flow. The diverted flow should not be less than the design discharge of the hydropower station and the amount of the sediment entering the hydraulic system should be minimum. In this study a physical model of a Tyrolean weir was constructed at the Hydromechanics Laboratory and by varying the dimensions of the various components of this system / the length, the inclination angle of the rack and the distance between the rack bars, the amount of water and sediment entering the system were measured for a wide range of discharges. The experiments were conducted in two stages. In the first stage the tests were made with only water, and in the second stage, water and sediment having different gradation were used. Applying dimensional analysis to the related parameters of the system dimensionless terms were defined for water capture efficiency and discharge coefficient of the system, and their variations with the relevant parameters were plotted. Using these diagrams one can determine the amount of water to be diverted by a Tyrolean weir of known geometry and main channel flow.

Tyrolean type water-intake structures are commonly used on mountain rivers to supply water to hydropower stations. The amount of water to be diverted from the main channel is the major concern in these kind of structures and should not be less than the design discharge. In this study a physical model of a Tyrolean type water-intake structure was built at the laboratory and the diverted flow from the main channel through the intake structure having steel racks and perforated plates of different types were measured. The experiments were conducted in two stages. In the first stage the tests were carried out with only steel racks having three different bar openings and slopes, and in the second stage, perforated screens of three different circular openings and screen slopes were used. Applying dimensional analysis to the related parameters of the system the dimensionless terms were defined for the water capture efficiency and discharge coefficient of the system, and their variations with the relevant parameters were plotted. Using these diagrams one can determine the amount of water to be diverted by a Tyrolean weir of known geometry and main channel discharge.