The intensive research on sediment transport indicates a need of an appropriate equation for predicting the total sediment load in rivers to manage reservoirs, operate dam and design in-stream hydraulic structures. None of the available equations in sediment transport has gained universal acceptance for predicting the total sediment transport rate. These facts indicate the need of a general formula to represent all these formula for predicting the sediment transport rate. The first goal of this dissertation is to find a unified total sediment transport equation for all rivers. On the other hand, scour around hydraulic structures such as spur dikes and bridge piers can be a serious problem that weakens structural stability. An investigation on the turbulent flow field and turbulence distribution around such hydraulic structures is essential to understand the mechanism of local scour and to determine which turbulence properties affect the local sediment transport. In addition, a universal turbulent model that is valid for all cases of turbulent flow in open channels does not exist. This dissertation thoroughly examined the turbulent flow field and turbulence distribution around a series of three dikes. The goal is to determine the significant turbulent properties for predicting the local sediment transport rate and to identify the appropriate turbulence model for simulating turbulent flow field around the dikes.To develop a general unified total load equation, this study evaluates 31 commonly used formulae for predicting the total sediment load. This study attributes the deviations of calculated results from different formulae to the stochastic properties of bed shear stresses and assumes that the bed shear stress satisfies the log- normal distribution. At any given bed shear stress, Monte Carlo simulation is applied to each equation, and a set of bed shear stresses are randomly generated. Total sediment load generated from each Monte Carlo realization of all the equations are assembled to represent the samples of total sediment load predicted from all the equations. The statistical properties of the resultant total sediment loads (e.g. standard deviation, mean) at each given bed shear stress are calculated. Then, a unified total sediment load equation is obtained based on the mean value from all the equations. The results showed the mean of all the equations is a power function of dimensionless bed shear stress. Reasonable agreements with measurements demonstrate that the unified equation is more accurate than any individual equation for predicting the total sediment load.An experimental study and numerical simulation of the flow field and local scour around a series of spur dikes is performed in a fixed flat bed and scoured bed condition. A micro-Acoustic Doppler Velocimeter (ADV) is used to measure the instantaneous velocity field in all the three spatial directions and the measured velocity profiles are used to calculate the turbulence properties. Results show that the local scour develops around the first dike. Turbulence intensity together with the mean velocity in the vertical direction measured at the flat bed closely correlates to the scour depth. In addition, the maximum bed shear stress, occurring at the tip of the second dike in the three-dike series, does not correspond to the maximum scour. Large bed load transport due to bed shear stress may not initiate bed scouring, but turbulence bursts (e.g. sweeps and ejections) will entrain sediment from bed surface and develop the local scour.A three-dimensional numerical model FLOW-3D is used to simulate the turbulent flow field around a series of spur dikes in flat and scoured bed. This study examines Prandtl's mixing length model, one equation model, standard two-equation model, Renormalization-Group (RNG) model, and Large Eddy Simulations (LES) turbulence model. The Prandtl's mixing length model and one equation model are not applicable to flow field around dikes. Results of mean flow field by using the standard two-equation model, and RNG turbulence model are close to the experimental data, however the simulated turbulence properties from different turbulent model deviate considerably. The calculated results from different turbulence models show that the RNG model best predicts the mean flow field for this series of spur dikes. None of the turbulence closure models can predict accurate results of turbulence properties, such as turbulence kinetic energy. Based on those results, this study recommends the use of RNG model for simulating mean flow field around dikes. Further improvements of FLOW-3D model is needed for predicting turbulence properties near this series of spur dikes under various flow conditions.

A set of laboratory experiments was carried out to distinguish flow characteristics(bed origin, shear velocity, turbulence intensity, turbulent kinetic energy) between beds of differing gravel angularity. Ten vertical profiles of velocity measurements were taken from angular and rounded fixed gravel beds with a 16 MHz micro acoustic Doppler velocimeter (ADV) sampling at 50 Hz. Both gravel beds had a bottom slope of 0.2% and were in the intermediate - roughness scale. Shear velocities were calculated using three common methods: St Venant, Reynolds stress, and Clauser. The Reynolds stress method resulted in the closest visual match to turbulence distributions proposed by others. The bed origin was found to be on average 0.24D50 and 0.21D50 for the angular and rounded gravel beds respectively. These differences, however, were not statistically significant. Turbulence intensity within 20% of the bed showed considerable scatter. The difficult measuring conditions likely prevented the ADV to detect significant differences of turbulence intensity in the longitudinal and transverse directions between the two gravel beds. But the ADV measurements in the vertical direction may well resolve turbulence even in difficult flow conditions (determined by acoustic Doppler performance curve formulation). For the vertical direction, the angular gravel bed showed an increase in TImax that extended throughout the profile. The increased turbulence intensity had a concomitant effect of increasing the turbulent kinetic energy for the angular bed.

The bluehead chub (Nocomis leptocephalus) is a keystone species, an ecosystem engi- neer that constructs mounded gravel nests for spawning. Chubs provide benefits for other spawning fishes, predators, and benthic organisms through their nest construction. This study seeks to apply sediment transport models to find incipient motion criteria and erosion susceptibility of chubs nests. Field water flow velocities were measured with an acoustic Doppler velocimeter (ADV) in Tom's Creek, Blacksburg, Virginia, USA. ADVs are often used to collect in-situ turbulent velocity data. In almost all applications of ADVs, erroneous spikes are recorded during collection, which can significantly distort turbulence statistics de- rived from velocity fluctuations. In this study, a bivariate kernel density estimation despiking algorithm is compared to a novel univariate simplification developed as part of this work. Despiking methods are evaluated using field ADV and direct numerical simulation (DNS) data of a turbulent boundary layer. Visual assessment of despiked velocity time series and power spectra and corresponding changes in statistical moments, as well as response to arti- ficial spiking of DNS data, yield valid performance of the univariate method. After despiking chub nest data, multiple methods of finding bed shear stress from velocity vertical profiles are evaluated. Bed shear stress is found over the profile of 26 field nests. The ambient to peak flow stress amplification due to a nest's bed protrusion is found to be a proportion of τ = 1.66τ to determine a critical ambient Shields parameter of approximately τ∗ = 0.03 pa c,a for nests. / Master of Science / The bluehead chub is a keystone species, an ecosystem engineer that constructs mounded gravel nests for spawning. These nests benefit numerous other species within their habitat. The possibility of nest erosion is characterized in this study using existing sediment transport principles. Nest flow characteristics are measured using an acoustic Doppler velocimeter (ADV). ADVs are often the instrument of choice in measuring water velocity. The high resolution of these devices can capture turbulent flows well, however data collection often results in inclusion of erroneous spikes in velocity. These spikes represent points deemed impossible due to their sudden change in velocity magnitude. Spikes do not have a large effect on average velocities of ADV data, but can influence turbulence statistics that describe the turbulent fluctuations in flow velocities. To remove spikes, multiple methods incorporate different outlier detection principles. This study evaluates a popular method that employs a two-dimensional kernel density estimation (KDE) algorithm. A recent study suggested the possible simplification of this method to use a one-dimensional kernel density estimation instead. Both the 1D and 2D methods are evaluated in this study in how they filter ADV data and whether it results in a clean, improved velocity time series that would be expected in turbulent flows. A novel 1D KDE method was also developed as part of this study. The new method is found to produce the most reliable filtering. Despiked ADV data is used to characterize the hydraulics over bluehead chub nests sampled in Tom's Creek, Blacksburg, Virginia, USA. Hydraulics are evaluated to see if ambient flow upstream of a nest can characterize the flow characteristics over the peak of the nest. Shear stress amplification over the nest is used to find a critical threshold for nest erosion based on ambient flows. Stress amplification in the ambient flow to the peak over the nest is found to be a simple proportion, and amplification factor of 1.66. This means we expect shear stress over the peak of a chub nest to be 1.66 times greater than the ambient bed shear stress upstream of the nest. This amplification factor can be used with existing methods to calculate critical non- dimensional shear stress values, also known as the critical Shields stress. After accounting for the amplification factor of 1.66, a critical Shields of approximately 0.03 is found.

Supercritical fluid jets provide a complex flow pattern and are present in many engineering applications. To date, studies have focused on wall jets, free jets, and two-dimensional offset jets. As a result, our understanding of three-dimensional offset jets is lacking. A deeper understanding of three-dimensional offset jets is important as they are seen in many engineering applications. Understanding the flow patterns of three-dimensional offset jets will aid hydraulic engineers to reduce anthropogenic effects when designing new and rehabilitating older hydraulic structures. The purpose of this study was to evaluate the effects of tailwater level and asymmetry ratio on three-dimensional offset jets. A physical model was constructed and three sets of experiments were conducted. Each set of experiments evaluated the effects of the Reynolds number, tailwater level, or asymmetry ratio. Velocity measurements were taken with an acoustic Doppler velocimeter. The acoustic Doppler velocimeter measured all three components of velocity which allowed the calculation of all six components of Reynolds shear stresses and ten components of triple velocity correlation. The effects of Reynolds number, tailwater level, and asymmetry ratio on streamwise flow development, distributions of mean velocities, and distribution of turbulence statistics were evaluated. Reynolds number effects were found to be insignificant at Reynolds number greater than 53,000. Two different trends were observed in the behavior of three-dimensional offset jets at different tailwater levels. At low tailwater levels the jet will not reattach to the channel bottom as it does at higher tailwater levels. Increasing the asymmetry ratio of an offset jet will make the jet curve towards the channel wall and bottom faster. Once reattached to the wall the velocity decay rate is greatly reduced. The results found in this study will be useful to a hydraulic engineer designing new or rehabilitating older hydraulic structures which have flow characteristics similar to that of three-dimensional offset jets. The data acquired during this study adds to the available data usable for calibration and validation of turbulence models. All three components of velocity were measured simultaneously which allowed to calculation of the six Reynolds shear stresses and ten triple velocity correlation terms. All velocities and turbulence statistics in this study were measured simultaneously which provides a data set that has rarely been seen before.

Hydraulically induced scour of the streambed at the base of bridge piers is the leading cause of bridge failures. Despite the significant scientific efforts towards the solution of this challenging engineering problem, there are still no reliable tools for the prediction and mitigation of bridge scour. This shortcoming is attributed to the lack of understanding of the physics behind this phenomenon. The experimental studies that attempted the physical investigation of bridge scour in the past have faced two main limitations: i) The characterization of the dynamic interaction between the flow and the evolving bed that is known to drive scour, was not possible due to the limitations in the available instrumentation and the significant experimental difficulties; ii) Most of the existing literature studies are based on the findings of laboratory experiments whose scale is orders of magnitudes smaller compared to bridges in the field, while the scale effects on the scour depth have never been quantified. The objective of this research was to enhance the existing understanding of the phenomenon by tackling the aforementioned experimental challenges. To accomplish this, the first part of this work involved the development of a new underwater photogrammetric technique for the monitoring of evolving sediment beds. This technique is able to obtain very high resolution measurements of evolving beds, thus allowing the characterization of their dynamic properties (i.e. evolving topography and scour rates) and overcoming existing experimental limitations. Secondly, the underwater photogrammetric technique was applied on a bridge scour experiment, of simple geometry, and the dynamic morphological characteristics of the phenomenon were measured. The detailed measurements along with reasonable comparisons with descriptions of the flow, from past studies, were used to provide insight on the interaction between the flow and the bed and describe quantitatively the mechanisms of scour. Finally, the scale effects on scour were studied via the performance of two experiments under near-prototype conditions. In these experiments the effects of the Reynolds number on the flow and the scour were quantified and implications concerning existing small-scale studies were discussed. / Ph. D.

Yes / This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles, including Reynolds stress, turbulence intensity and bursting analysis of open channel flow. Different vegetation densities have been built between the adjacent vegetations, and the flow measurements are taken using acoustic Doppler velocimeter (ADV) at the locations within and downstream of the vegetation panel. Three different tests are conducted, where the first test has compact vegetations, while the second and the third tests have open spaces created by one and two empty vegetation slots within the vegetated field. Observation reveals that over 10% of eddies size is generated within the vegetated zone of compact vegetations as compared with the fewer vegetations. Significant turbulence structures variation is also observed at the points in the non-vegetated row. The findings from burst-cycle analysis show that the sweep and outward interaction events are dominant, where they further increase away from the bed. The effect of vegetation on the turbulent burst cycle is mostly obvious up to approximately two-third of vegetation height where this phenomenon is also observed for most other turbulent structure. / The full text will be available at the end of the publisher's embargo period: 1st Feb 2025

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The designs of pump intake structures are generally verified by means of a hydraulic model study to ensure the structure will operate without large air or swirl entraining vortices. This is an expensive and time consuming process. The popularity of Computational Fluid Dynamics (CFD) is ever increasing in the engineering world and the use thereof in the modelling of flows in pump intake structures is just one of the many areas of focus. The use of a validated CFD model in the design phase of pump intakes would be beneficial, and ideally would reduce the frequency of requiring hydraulic model studies. This study investigates the applicability of using a 3 dimensional CFD model as a design tool by validation with a physical model. A physical model of a simple pump intake was available and with a few modifications the flow conditions were significantly improved. The quantitative validation of the CFD model was carried out by means of comparing corresponding point velocity magnitudes. An Acoustic Doppler Velocimeter (ADV) was used in the physical model. The data obtained were successfully filtered to remove noise and other disturbances. The qualitative validation was done by means of photographs and observations. The photographs made use of illuminated tracer particles to identify flow patterns. The CFD model compares well qualitatively, but the velocity magnitudes are not yet sufficiently reliable. It is recommended that the CFD model can be used for qualitative studies, but future research should focus on the accuracy of the CFD model. Using higher resolution velocity measurements in the physical model by means of other types of instruments, a better comparison can be made, as well as enabling validation of the ADV readings. / AFRIKAANSE OPSOMMING: Die ontwerpe van die pomp inname strukture word gewoonlik bevestig deur middel van 'n hidrouliese model studie om lug-intrekking te minimeer. Dit is 'n duur en tydrowende proses . Die gebruik van Computational Fluid Dynamics ( CFD ), ‘n tipe numeriese modelle neem toe in die ingenieurswese wêreld. Die gebruik daarvan in die modellering van vloei in pomp inname strukture is net een van die vele areas van toepassing . Die gebruik van 'n betroubare CFD model in die ontwerp fase van pomp innames sal voordelig wees , en ideaal sou die noodaaklikheid van fisiese hidrouliese model studies verminder. Hierdie studie ondersoek die toepaslikheid van die gebruik van 'n 3 -dimensionele model CFD model as 'n ontwerp instrument deur bevestiging met 'n fisiese model . 'n Eenvoudige pomp-inname model was beskikbaar en het met ‘n paar veranderinge die vloei toestande aansienlik verbeter . Die kwantitatiewe bevestiging van die CFD model is uitgevoer deur middel van vergelyking van korresponderende punt snelheid groottes. In die fisiese model is die snelhede met 'n Akoestiese Doppler Velocimeter (ADV) gemeet. Die data wat verkry is suksesvol gefiltreer om geraas en ander versteurings te verwyder . Die kwalitatiewe bevestiging is gedoen deur middel van foto's en waarnemings. In die foto's is gebruik gemaak van verligte spoor deeltjies om vloei patrone te identifiseer. Die CFD model vergelyk kwalitatief goed, maar die snelheid groottes is nog nie voldoende betroubaar nie. Dit word aanbeveel dat die CFD model gebruik kan word vir kwalitatiewe studies, maar toekomstige navorsing behoort te fokus op die verbeteringe van dieakkuraatheid van die CFD model. Met behulp van 'n hoër resolusie snelheid metings van die fisiese model, deur middel van ander tipe instrumente, kan 'n beter vergelyking gemaak word , sowel as die geldigheid van die ADV lesings in staat te stel.

An experimental study was designed to investigate the effect of different parameters on the development and structure of turbulent 3D offset jets. The present investigation considered the effects of offset height ratio, expansion ratio, surface roughness and rib placement on the flow dynamics of a turbulent 3D offset jet. The velocity measurements were performed using an acoustic Doppler velocimetry (ADV) and particle image velocimetry (PIV). Measurements were conducted within the symmetry and lateral planes. For the PIV technique, the measurements in the symmetry and lateral planes were conducted over a streamwise range of 0 ≤ x/bo ≤ 80 and 12 ≤ x/bo ≤ 60, respectively (where bo is the nozzle height). Likewise, velocity measurements using the ADV technique were conducted over a range of 4 ≤ x/bo ≤ 45 in both the symmetry and lateral planes. The velocity measurements were analyzed using both one-point and multi-point statistics. The one-point statistics included profiles of the mean velocities, Reynolds stresses and some of the budget terms in the turbulent kinetic energy transport equation. The quadrant analysis technique was used to investigate the dominant events that contribute towards the Reynolds shear stress. The two-point correlation analysis was used to investigate how the turbulence quantities are correlated. Information obtained from the two-point correlation analysis was also used to investigate the inclination of vortical structures within the inner and outer shear layers of the 3D offset jet. The direction of the positive mean shear gradient played an active role in the inclination of these vortical structures within the inner and outer shear layers. The reattachment process resulted in the breakdown of these structures within the developing region. Similarly, various length scales were estimated from these structures. The proper orthogonal decomposition was used to examine the distribution of the turbulent kinetic energy within the offset jet flow. Also, the dynamic role of the large scale structures towards the turbulent intensities, turbulent kinetic energy and Reynolds shear stress was investigated. / October 2016

Os mecanismos de transposição de peixes (MTP) são estruturas ou sistemas que possibilitam a migração da ictiofauna entre as partes de jusante/montante/jusante de uma barragem. As escadas para peixes representam um dos tipos de MTP mais conhecidos no mundo e apresentam diversas configurações geométricas. A escolha do tipo de escada deve atender às características natatórias dos peixes selecionados para transporem o obstáculo. Para algumas espécies, como o salmão, já se conhecem geometrias adequadas, entretanto, para a maioria das espécies isto não ocorre e muitos projetos têm demonstrado desempenho insatisfatório. No Brasil, encontra-se uma imensa diversidade de espécies de peixes, cujas características natatórias diferem em muito das apresentadas pelos salmonídeos. Este fato, associado à crescente exigência da implantação de MTP nos barramentos, através de leis estaduais ambientais, torna necessária a definição de estruturas adequadas à ictiofauna brasileira. A validação dos critérios de projeto passa, obrigatoriamente, por estudos que avaliem as características hidráulicas das estruturas propostas e a interação do fluxo com os padrões natatórios da ictiofauna. O número de pesquisas relacionadas ao funcionamento hidráulico de escadas para peixes vem crescendo, entretanto ainda são insuficientes, não existindo um consenso sobre os critérios, seja para sua caracterização completa, seja para definir sobre quais parâmetros devem ser considerados. Os padrões de turbulência do escoamento em escadas para peixes, cujas características supõem-se relacionarem-se com o grau de aceitação ou rejeição das espécies, são praticamente desconhecidos. Neste trabalho realizou-se a caracterização hidráulica através do estudo experimental, de três tipos de escadas para peixes: (1) com ranhura vertical; (2) com descarregador de superfície e (3) com orifício de fundo. As estruturas foram construídas nos laboratórios do Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul – IPH/UFRGS e no Laboratório Nacional de Engenharia Civil – LNEC – Portugal. As seguintes medições foram realizadas: velocidades em três direções, em diferentes planos dos tanques, com velocímetros acústicos Doppler (ADV) e níveis de água da superfície livre com pontas linimétricas e réguas graduadas. Para a estrutura com ranhura vertical ainda foram medidas as pressões médias e suas flutuações, junto ao fundo do canal, com transdutores piezoresistivos. Para cada uma das estruturas realizaram-se ensaios com três descargas. Além de definidas as características médias do escoamento, os dados de velocidades, que passaram por um processo de aplicação de filtros sem substituição, possibilitaram a avaliação de parâmetros de turbulência, entre eles a energia cinética da turbulência, a intensidade da turbulência e as tensões de Reynolds. No modelo da escada para peixes com ranhuras verticais verificou-se que os parâmetros hidráulicos estão de acordo com estruturas similares da bibliografia, entre eles, coeficiente de descarga, vazão adimensional e coeficiente de cisalhamento. Os campos de pressão junto ao fundo refletem o comportamento da superfície livre do escoamento. Através do mapeamento das velocidades dentro do tanque da escada do tipo ranhura vertical, foi possível caracterizar as duas zonas de recirculação e a região do jato principal. Os máximos valores médios de velocidade encontram-se na seção da ranhura, não excedendo 1,00 m/s (no modelo). Além disso, foi possível reconhecer as regiões de maior energia cinética da turbulência que apresentaram valores de até 1000 cm2/s2 na região do jato principal, as quais coincidem com as zonas de maiores tensões de Reynolds da ordem de até 30 N/m2. A partir das velocidades médias e em função das velocidades de nado dos peixes obtidos na literatura, foi possível a identificação de locais que atuam como “barreiras” ao deslocamento de determinada espécie. A avaliação qualitativa do comportamento da trajetória dos peixes dentro dos tanques mostrou-se de acordo com a definição destas “barreiras” hidráulicas e com a avaliação do comportamento dos campos de energia cinética da turbulência e das tensões de Reynolds. No modelo da escada do tipo descarregador de superfície observaram-se as máximas velocidades médias sobre o descarregador, com valores de até 1,73 m/s. Verifica-se que na maior parte do tanque as velocidades médias não ultrapassam 40% da velocidade potencial. Foram encontrados valores de energia cinética da turbulência até 2000 cm2/s2, com valores na maior parte do tanque em torno de 200 cm2/s2. Quanto aos campos de tensões de Reynolds, têm-se, na maior parte do tanque, os valores entre −5 e 5 N/m2, sendo que na região do jato mergulhante, os valores chegam até 30 N/m2. Na escada com orifícios de fundo verificaram-se as maiores velocidades médias nos planos sob influência do fluxo principal proveniente do orifício. Não foi possível a medição da velocidade na seção da abertura, sendo que os valores medidos no tanque não ultrapassaram 50% da velocidade potencial. Os máximos valores de energia cinética da turbulência atingem até 2000 cm2/s2 junto ao fundo, enquanto na região central do tanque, o valor médio é um pouco inferior a 200 cm2/s2. Os valores de tensão de Reynolds encontram-se entre −30 e 30 N/m2, com a maioria das regiões entre −5 e 5 N/m2. Os valores máximos e médios de energia cinética da turbulência e tensões de Reynolds para os modelos com descarregador de superfície e com orifício de fundo encontram-se na mesma faixa. Isto indica que, sob o ponto de vista técnico, possivelmente o critério de escolha entre essas duas estruturas recai nas características da ictiofauna. A passagem com ranhura vertical permite a escolha da profundidade preferencial de nado. No entanto, nessa estrutura, verificase que as componentes médias e turbulentas, nas regiões de descanso, comparando-as com os valores máximos do jato principal, são superiores proporcionalmente, às observadas nas zonas de recirculação das outras duas estruturas. As informações biológicas disponíveis na literatura não permitem a definição de condições preferenciais em relação aos parâmetros de turbulência entre as estruturas aqui avaliadas. No entanto, as informações obtidas nesse trabalho indicam que a energia cinética da turbulência e as tensões de Reynolds podem ser indicativos da tolerância ou preferência dos peixes até certos níveis de turbulência. / Fish facilities are structures or systems that enable fish passage through dams or obstructions. Fishways represent one of the most common fish facilities types worldwide, presenting different geometries and designs. The choice and design of these structures must attend the fish swimming performance and biological characteristics. For some species, as salmon, there are defined designs that can be successfully applied, however, that does not occur for the majority of the species and many projects have showed unsatisfactory efficiency. In Brazil, there is an immense diversity of fish species, whose swimming characteristics are strongly different than the other known species like the salmons. This fact, associated with the increasing requirement of fish facilities implantation in dams, mainly through environmental State Laws, requires the definition of structures adapted to the Brazilian fish. The design criteria validation needs, necessarily, studies to evaluate hydraulic characteristics on structure proposals and the interaction of the flow with swimming abilities. The number of researches related to the hydraulic functioning of fishways is increasing, however they are still insufficient and there is not a consensus on the criteria, either for its complete characterization, either to define which parameters should be considered. The flow turbulence patterns in fishways, whose characteristics are assumed to be related with the degree of acceptance or rejection of the species, are practically unknown. In this study a hydraulic characterization was carried out through an experimental study, including three kinds of fishways: (1) with vertical slots; (2) with rectangular notches and (3) with bottom orifices. The facilities were set up in the Hydraulic Research Institute of the Federal University of Rio Grande do Sul (IPH/UFRGS) and in the National Laboratory of Civil Engineering – LNEC - Portugal. The following measurements were carried out: three-direction velocities, in a 3D-mesh in one pool of each structure, with Acoustic Doppler Velocimeters and water level of the free surface with a point gauge and scales. In the vertical slot fishway it was carried out complementary measurements of pressure in the bottom of the channel, with transducers. For each structure three discharges were tested. Besides defining the mean flow characteristics, the velocity time data, filtered (through a digital process) without substitution, allowed to analyze some turbulence parameters, as turbulence kinetic energy, turbulence intensity and Reynolds’ shear stresses. In the vertical slot fishway model it was verified that the hydraulic parameters are in agreement with similar structures of the literature, among them, discharge coefficient, adimensional discharge and friction factor. The bottom pressure field agrees with the behavior of the free-surface flow. Two recirculation zones and the area of the main jet were characterized through the velocities distribution inside the vertical slot fishway pool. The maximum mean velocity values were found in the slot section, not exceeding 1.00 m/s (in the model). Moreover, it was possible to recognize the areas with larger turbulence kinetic energy that presented values of up to 1000 cm²/s² in the main jet area, which correspond to the largest Reynolds’ shear stresses values of up to 30 N/m². Considering mean velocities data and fish swimming capabilities, it was possible to identify regions that are insurmountable by the fish. The qualitative approach of the fish trajectory inside the structure agrees with the insurmountable regions described through mean velocities and with the distribution of turbulence kinetic energy and Reynolds’ stresses. In the fishway model with rectangular notches, the maximum mean velocities were observed on the weir, with values of up to 1.73 m/s. In the major part of the pool, mean velocities do not surpass 40% of the potential velocity. Values up to 2000 cm²/s² for turbulence kinetic energy were found, with values in the major part of the pool close to 200 cm²/s². For Reynolds’ stresses, the major part of the structure works with values in the range of −5 and 5 N/m², and in the jet entrance pool region the values are of up to 30 N/m². In the fishway with bottom orifices the largest mean velocities were verified in the plans under influence of the main flow connecting consecutive orifices. The measurement of the velocities in the orifice section was not possible and the values measured in the pool did not exceed 50% of the potential velocity. The maximum values of turbulence kinetic energy reached up to 2000 cm²/s² close to the bottom channel, while in the central area of the pool, the mean value is lower than 200 cm2/s2. The values of Reynolds’ shear stresses are between −30 and 30 N/m2, with the major part between−5 and 5 N/m2. The maximum and mean values of turbulence kinetic energy and Reynolds’ stresses in the models with rectangular notches and with orifice are in the same range. It indicates that the choice between these two structures relapses in the fish swimming characteristics. The passage with vertical slot allows the choice of the swimming depth preference. However, in the resting areas of this structure, it is verified that the mean and turbulent components when compared with the maximum values of the main jet, are higher proportionally, to the ones observed in the recirculation zones of the other two structures. The biological information available in the literature does not allow the definition of preferential conditions in relation to the turbulence parameters among the structures here appraised. However, the information obtained in this work indicates that the turbulence kinetic energy and Reynolds’ shear stress can be indicatives of the tolerance or preference of the fish to certain turbulence levels.

Os mecanismos de transposição de peixes (MTP) são estruturas ou sistemas que possibilitam a migração da ictiofauna entre as partes de jusante/montante/jusante de uma barragem. As escadas para peixes representam um dos tipos de MTP mais conhecidos no mundo e apresentam diversas configurações geométricas. A escolha do tipo de escada deve atender às características natatórias dos peixes selecionados para transporem o obstáculo. Para algumas espécies, como o salmão, já se conhecem geometrias adequadas, entretanto, para a maioria das espécies isto não ocorre e muitos projetos têm demonstrado desempenho insatisfatório. No Brasil, encontra-se uma imensa diversidade de espécies de peixes, cujas características natatórias diferem em muito das apresentadas pelos salmonídeos. Este fato, associado à crescente exigência da implantação de MTP nos barramentos, através de leis estaduais ambientais, torna necessária a definição de estruturas adequadas à ictiofauna brasileira. A validação dos critérios de projeto passa, obrigatoriamente, por estudos que avaliem as características hidráulicas das estruturas propostas e a interação do fluxo com os padrões natatórios da ictiofauna. O número de pesquisas relacionadas ao funcionamento hidráulico de escadas para peixes vem crescendo, entretanto ainda são insuficientes, não existindo um consenso sobre os critérios, seja para sua caracterização completa, seja para definir sobre quais parâmetros devem ser considerados. Os padrões de turbulência do escoamento em escadas para peixes, cujas características supõem-se relacionarem-se com o grau de aceitação ou rejeição das espécies, são praticamente desconhecidos. Neste trabalho realizou-se a caracterização hidráulica através do estudo experimental, de três tipos de escadas para peixes: (1) com ranhura vertical; (2) com descarregador de superfície e (3) com orifício de fundo. As estruturas foram construídas nos laboratórios do Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul – IPH/UFRGS e no Laboratório Nacional de Engenharia Civil – LNEC – Portugal. As seguintes medições foram realizadas: velocidades em três direções, em diferentes planos dos tanques, com velocímetros acústicos Doppler (ADV) e níveis de água da superfície livre com pontas linimétricas e réguas graduadas. Para a estrutura com ranhura vertical ainda foram medidas as pressões médias e suas flutuações, junto ao fundo do canal, com transdutores piezoresistivos. Para cada uma das estruturas realizaram-se ensaios com três descargas. Além de definidas as características médias do escoamento, os dados de velocidades, que passaram por um processo de aplicação de filtros sem substituição, possibilitaram a avaliação de parâmetros de turbulência, entre eles a energia cinética da turbulência, a intensidade da turbulência e as tensões de Reynolds. No modelo da escada para peixes com ranhuras verticais verificou-se que os parâmetros hidráulicos estão de acordo com estruturas similares da bibliografia, entre eles, coeficiente de descarga, vazão adimensional e coeficiente de cisalhamento. Os campos de pressão junto ao fundo refletem o comportamento da superfície livre do escoamento. Através do mapeamento das velocidades dentro do tanque da escada do tipo ranhura vertical, foi possível caracterizar as duas zonas de recirculação e a região do jato principal. Os máximos valores médios de velocidade encontram-se na seção da ranhura, não excedendo 1,00 m/s (no modelo). Além disso, foi possível reconhecer as regiões de maior energia cinética da turbulência que apresentaram valores de até 1000 cm2/s2 na região do jato principal, as quais coincidem com as zonas de maiores tensões de Reynolds da ordem de até 30 N/m2. A partir das velocidades médias e em função das velocidades de nado dos peixes obtidos na literatura, foi possível a identificação de locais que atuam como “barreiras” ao deslocamento de determinada espécie. A avaliação qualitativa do comportamento da trajetória dos peixes dentro dos tanques mostrou-se de acordo com a definição destas “barreiras” hidráulicas e com a avaliação do comportamento dos campos de energia cinética da turbulência e das tensões de Reynolds. No modelo da escada do tipo descarregador de superfície observaram-se as máximas velocidades médias sobre o descarregador, com valores de até 1,73 m/s. Verifica-se que na maior parte do tanque as velocidades médias não ultrapassam 40% da velocidade potencial. Foram encontrados valores de energia cinética da turbulência até 2000 cm2/s2, com valores na maior parte do tanque em torno de 200 cm2/s2. Quanto aos campos de tensões de Reynolds, têm-se, na maior parte do tanque, os valores entre −5 e 5 N/m2, sendo que na região do jato mergulhante, os valores chegam até 30 N/m2. Na escada com orifícios de fundo verificaram-se as maiores velocidades médias nos planos sob influência do fluxo principal proveniente do orifício. Não foi possível a medição da velocidade na seção da abertura, sendo que os valores medidos no tanque não ultrapassaram 50% da velocidade potencial. Os máximos valores de energia cinética da turbulência atingem até 2000 cm2/s2 junto ao fundo, enquanto na região central do tanque, o valor médio é um pouco inferior a 200 cm2/s2. Os valores de tensão de Reynolds encontram-se entre −30 e 30 N/m2, com a maioria das regiões entre −5 e 5 N/m2. Os valores máximos e médios de energia cinética da turbulência e tensões de Reynolds para os modelos com descarregador de superfície e com orifício de fundo encontram-se na mesma faixa. Isto indica que, sob o ponto de vista técnico, possivelmente o critério de escolha entre essas duas estruturas recai nas características da ictiofauna. A passagem com ranhura vertical permite a escolha da profundidade preferencial de nado. No entanto, nessa estrutura, verificase que as componentes médias e turbulentas, nas regiões de descanso, comparando-as com os valores máximos do jato principal, são superiores proporcionalmente, às observadas nas zonas de recirculação das outras duas estruturas. As informações biológicas disponíveis na literatura não permitem a definição de condições preferenciais em relação aos parâmetros de turbulência entre as estruturas aqui avaliadas. No entanto, as informações obtidas nesse trabalho indicam que a energia cinética da turbulência e as tensões de Reynolds podem ser indicativos da tolerância ou preferência dos peixes até certos níveis de turbulência. / Fish facilities are structures or systems that enable fish passage through dams or obstructions. Fishways represent one of the most common fish facilities types worldwide, presenting different geometries and designs. The choice and design of these structures must attend the fish swimming performance and biological characteristics. For some species, as salmon, there are defined designs that can be successfully applied, however, that does not occur for the majority of the species and many projects have showed unsatisfactory efficiency. In Brazil, there is an immense diversity of fish species, whose swimming characteristics are strongly different than the other known species like the salmons. This fact, associated with the increasing requirement of fish facilities implantation in dams, mainly through environmental State Laws, requires the definition of structures adapted to the Brazilian fish. The design criteria validation needs, necessarily, studies to evaluate hydraulic characteristics on structure proposals and the interaction of the flow with swimming abilities. The number of researches related to the hydraulic functioning of fishways is increasing, however they are still insufficient and there is not a consensus on the criteria, either for its complete characterization, either to define which parameters should be considered. The flow turbulence patterns in fishways, whose characteristics are assumed to be related with the degree of acceptance or rejection of the species, are practically unknown. In this study a hydraulic characterization was carried out through an experimental study, including three kinds of fishways: (1) with vertical slots; (2) with rectangular notches and (3) with bottom orifices. The facilities were set up in the Hydraulic Research Institute of the Federal University of Rio Grande do Sul (IPH/UFRGS) and in the National Laboratory of Civil Engineering – LNEC - Portugal. The following measurements were carried out: three-direction velocities, in a 3D-mesh in one pool of each structure, with Acoustic Doppler Velocimeters and water level of the free surface with a point gauge and scales. In the vertical slot fishway it was carried out complementary measurements of pressure in the bottom of the channel, with transducers. For each structure three discharges were tested. Besides defining the mean flow characteristics, the velocity time data, filtered (through a digital process) without substitution, allowed to analyze some turbulence parameters, as turbulence kinetic energy, turbulence intensity and Reynolds’ shear stresses. In the vertical slot fishway model it was verified that the hydraulic parameters are in agreement with similar structures of the literature, among them, discharge coefficient, adimensional discharge and friction factor. The bottom pressure field agrees with the behavior of the free-surface flow. Two recirculation zones and the area of the main jet were characterized through the velocities distribution inside the vertical slot fishway pool. The maximum mean velocity values were found in the slot section, not exceeding 1.00 m/s (in the model). Moreover, it was possible to recognize the areas with larger turbulence kinetic energy that presented values of up to 1000 cm²/s² in the main jet area, which correspond to the largest Reynolds’ shear stresses values of up to 30 N/m². Considering mean velocities data and fish swimming capabilities, it was possible to identify regions that are insurmountable by the fish. The qualitative approach of the fish trajectory inside the structure agrees with the insurmountable regions described through mean velocities and with the distribution of turbulence kinetic energy and Reynolds’ stresses. In the fishway model with rectangular notches, the maximum mean velocities were observed on the weir, with values of up to 1.73 m/s. In the major part of the pool, mean velocities do not surpass 40% of the potential velocity. Values up to 2000 cm²/s² for turbulence kinetic energy were found, with values in the major part of the pool close to 200 cm²/s². For Reynolds’ stresses, the major part of the structure works with values in the range of −5 and 5 N/m², and in the jet entrance pool region the values are of up to 30 N/m². In the fishway with bottom orifices the largest mean velocities were verified in the plans under influence of the main flow connecting consecutive orifices. The measurement of the velocities in the orifice section was not possible and the values measured in the pool did not exceed 50% of the potential velocity. The maximum values of turbulence kinetic energy reached up to 2000 cm²/s² close to the bottom channel, while in the central area of the pool, the mean value is lower than 200 cm2/s2. The values of Reynolds’ shear stresses are between −30 and 30 N/m2, with the major part between−5 and 5 N/m2. The maximum and mean values of turbulence kinetic energy and Reynolds’ stresses in the models with rectangular notches and with orifice are in the same range. It indicates that the choice between these two structures relapses in the fish swimming characteristics. The passage with vertical slot allows the choice of the swimming depth preference. However, in the resting areas of this structure, it is verified that the mean and turbulent components when compared with the maximum values of the main jet, are higher proportionally, to the ones observed in the recirculation zones of the other two structures. The biological information available in the literature does not allow the definition of preferential conditions in relation to the turbulence parameters among the structures here appraised. However, the information obtained in this work indicates that the turbulence kinetic energy and Reynolds’ shear stress can be indicatives of the tolerance or preference of the fish to certain turbulence levels.