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The Brazilian electric matrix is based on renewable sources of energy, and most of it comes from hydroelectric power plants, its structure is composed of a dam, a capture system, a spillway, and a powerhouse, in this installation are the water turbines The main types are Francis, Bulbo, Helix, Kaplan, and Pelton each one has particularity for dimensioning. In this context, the objective of the article is to carry out the classic design of a Kaplan turbine runner wheel and the computational design. For this, first, the runner wheel case study was defined considering those installed in Brazil, using as criteria the power energy efficiency. Later, based on the input data: flow, fall height, and runner rotation, the calculation memorial was developed, preliminary calculations to define the specific rotation, complementary calculations to determine the minimum runner flow, number of poles, specific design rotation, an outer diameter of the runner blade, hub diameter, the height of the distributor, solid shaft diameter, fluid flow velocity, profile lengths, and profile thickness. The Hydroelectric Power Plant case study was Luis Eduardo Magalhães, installed on the Tocantins River in the state of Tocantins, has five generator units with Kaplan runners of five blades and power of 180.5 MW each, the flow rate of 700 m³/s, drop height of 29 m and 100 revolutions per minute. The values obtained were organized in electronic spreadsheets and later the computational design of the runner was performed using CAD software. The dimensioned runner wheel has dimensional and power values similar to the case study. Thus, it is concluded that the application of the classic dimensioning allowed the design of the runner wheel containing five blades and power of 183.4 MW, and the computational design allowed us to visualize the similarities with the case study.

We propose a single non-dimensional expression for the wind and temperature vertical profiles in the atmospheric boundary layer (ABL). Two major reformulations are implemented from the generalized function for dimensionless wind and temperature gradients, so that the theory from previous studies may be extended above the surface layer. First, the thermal part of the wind shear is modified based on a surface temperature scale θ* and a thermal-characteristic height zh instead of the Obukhov length. Second, we introduce two new terms in the total Reynolds stress associated with the nonlinear parts of the thermal-mechanical stress, where coefficients α and β maybe describe wind profiles of the low-level jets. The proposed wind and temperature profiles are compared with the universal function in the surface layer and validated with Wangara's wind and temperature profiles up to a height of 2 km, and their measurements of surface turbulent fluxes of heat and momentum. One case of unstable and four cases of stable conditions are selected from the Wangara dataset, representing cases of convective, stratified, nocturnal jet and transition between the stratified and jet profiles. The proposed function has a good correlation in the five cases of temperature and wind profiles with RMSE better than 0.7 K and 0.7 m s-1 respectively. The coefficients zh and b associated with the linear part of Reynolds stress, and the coefficients α and β associated with the nonlinear part of Reynolds stress are analized, and their possible physical meanings are discussed.

The aim of this paper is to analyse the thermal effects in a wind tunnel experiment to simulate the planetary boundary layer (PBL). Experiments were performed in the wind tunnel of the Laboratory of Constructions Aerodynamics at the Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul State, Brazil. This wind tunnel is a closed return low-speed wind tunnel specifically designed for dynamic and static studies on civil construction models. As a novelty, one of the experimental sections of the wind tunnel was equipped with a metal sheet with Peltier elements coupled to it. In other words, thermal effects generating new flow patterns become feasible and open pathways to compare wind tunnel simulations to those in the PBL. Furthermore, measurements obtained with the smooth floor of the wind tunnel were repeated under the same conditions with the addition of the roughness in the floor, and the mechanical turbulence generated by the surface roughness significantly amplified the exchange of momentum and heat between the regions located in vertical direction of the wind tunnel boundary layer. In the presence of turbulent heat flux near the surface, thermal effects contribute to the increase of the turbulence intensity. Turbulent energy spectra for flow velocities and different heights were obtained using the Hilbert–Huang transform method, and the observed convective turbulence energy spectra behavior reproduced those measured in an unstable surface PBL.

Observations of the vertical and temporal structure of the nocturnal boundary layer before and after a transition from the weakly to the very stable regime have been presented in Part I. Here, similar transitions are investigated using a one-dimensional second-order closure numerical model, with an energy budget solved at the surface. The transition is driven by a decreasing mean wind at the top of the domain, and simulations with different cloud covers and surface thermal properties are considered. The time of the transition depends on the wind speed at the top of the domain and on the "coupling strength" between the surface and the atmosphere, which is affected by the cloud cover and surface thermal properties. The vertical profiles and temporal evolutions of the terms of the budgets of turbulent kinetic energy (TKE), heat flux and temperature variance are presented. Of these, only TKE budget presents the same dominant terms in both regimes. Absolute heat flux in the model is proportional to the cube of the wind speed in the very stable regime.

A caracterização do escoamento dentro da camada limite noturna é muito complexa, devido a fraca intensidade da turbulência. Nessa situação, o escoamento apresenta um caráter bi-estável, ou seja, ele apresenta um equilíbrio quente, o que ocorre quando a temperatura próxima à superfície se aproxima da temperatura dos níveis mais altos, e um equilíbrio frio, quando a temperatura do ar fica próxima à temperatura da superfície, isto está envolvido com o colapso da turbulência. Nos últimos anos tem-se utilizados muito de experimentos numéricos para o estudo e a representação da transição entre os escoamentos turbulento-laminar, devido aos mesmos serem controlados e portanto livre de fenômenos em escalas maiores que as turbulentas. Esse trabalho traz como objetivo realizar uma simulação numérica para verificar a transição do escoamento de um fluído, dentro de um canal fechado, sobre diferentes gradientes de temperatura. Para a realização do mesmo, utilizou-se o software CFD (do inglês \textit{computer fluid dynamics}) de código livre OpenFOAM$^{\circledR}$, juntamente com o solver \textit{buoyantPimpleFoam}. O modelo de turbulência adotado durante a simulação foi o LES (do inglês \textit{Large Eddy Simulation}). A simulação ocorreu por por um período de $3600$ s, sem a variação de temperatura entre as placas. Logo após foi acrescentado os gradientes de temperatura ($0$ K, $3$ K, $5$ K, $7$ K e $10$ K) e seguiu-se a simulação por mais $3600$ s. Observando o gráfico dos perfis de velocidade do escoamento até o centro do domínio, é possível identificar que o fluido encontra-se turbulento, e logo após o resfriamento ocorre o processo de laminarização do escoamento. Isto se deve a velocidade do fluido ser baixa ($0,1$ m s$^{-1}$) e ao gradiente de temperatura ser alto para essa velocidade. Conclui-se que é possível destruir a turbulência utilizando um gradiente de temperatura, de maneira a laminarizar o escoamento. Porém, ainda que isto ocorra, a turbulência não é eliminada por completa.

In this work a method to estimate turbulent kinetic energy dissipation rate (TKEDR) was presented. The technique uses the second-order structure function and Kolmogorov’s law for inertial subrange. This methodology was applied on both neutral and stable stratification wind tunnel data, where the frozen turbulence hypothesis was assumed. The experiments were made with Reynolds Number ranging from 10 3 up to 10 4 . The results show difference between the neutral and stable cases, but this gap decreases with the mean wind speed. Furthermore, TKEDR evaluated was used to describe the inertial subrange in the longitudinal velocity spectrum with a good agreement with the experimental data.

Wind tunnel experiments of thermally stratified flows are analyzed with the objective of determining the influence of the thermal stratification on turbulence-related quantities. The experimental apparatus consisted of an aluminum plate inserted at the bottom surface of the wind tunnel test section. In order to create a thermally stratified layer, the plate was cooled down to 5oC and the air entering the tunnel was kept at approximately 20oC. As the wind speed increases, such stable layer was soon destroyed. Data shows that quantities such as temperature, variances, dissipation rates and turbulent fluxes are substantially reduced when surface cooling is present and that such a reduction is enhanced for weak wind conditions, as these are cases that preserve the stratification. On the other hand, third and fourth order statistical moments, as well as the mean wind speed are much less affected by the stratification.

A laboratory simulation was assessed for its capacity to reproduce the actual conditions found in a microburst. In our experimental set-up, the flow was driven by combined impinging jet and density perturbations forcing with the aim of determining their relative influence on the overall microburst behavior and, in particular, the initiation and structural evolution of the resulting vortex. These results were compared with those reported in the previous simulation works. Such comparisons showed that the laboratory model may satisfactorily reproduce relevant aspects of a microburst. An expression for the characteristic microburst propagation velocity was derived, accounting for the combined effects of forced velocity and flotation forces generated by the density difference, whose predictions are in good agreement with experimental data. The vortex structure is largely affected by the forcing type. The succession of vortex is best defined when a large density perturbation is combined with a weak jet impingement. The opposite configuration causes a main vortex to be succeeded by a wake where vortex structures are not clearly defined. Such behavior is caused by the fact that larger density perturbations inhibit the mean and turbulent velocities, favouring a well defined vortices structure, associated with weaker momentum diffusion.

In this study, the Hilbert-Huang transform was applied to experimental measurements performed in a wind tunnel to determine the frequency of occurrence of the spectral maximum. These maximum frequencies are associated with the time scale of the most energetic eddies and represent an important input parameter in the pollutants dispersion models. The values of the maximum frequencies obtained by the Hilbert-Huang marginal spectrum are compared with the vaues obtained by the traditionally used Fourier transform. The results show that the energy distribution calculated by both methods are very similar in the region of occurence of the spectral maximum, and for this reason, the maximum frequency values obtained by each method do not presente significant differences. Under determined hypothesis, the Hilbert-Huang transform provided physically more realistic maximum frequency values that those obtained using the Fourier transform.

In this study we analyze natural complex signals employing the Hilbert–Huang spectral analysis. Specifically, low wind meandering meteorological data are decomposed into turbulent and non turbulent components. These non turbulent movements, responsible for the absence of a preferential direction of the horizontal wind, provoke negative lobes in the meandering autocorrelation functions. The meandering characteristic time scales (meandering periods) are determined from the spectral peak provided by the Hilbert–Huang marginal spectrum. The magnitudes of the temperature and horizontal wind meandering period obtained agree with the results found from the best fit of the heuristic meandering autocorrelation functions. Therefore, the new method represents a new procedure to evaluate meandering periods that does not employ mathematical expressions to represent observed meandering autocorrelation functions.

Este trabalho relata um escoamento estratificado e turbulento, no qual a superficie e mais fria que o ambiente sobre ela. Dessa forma, verifica-se a influencia da estratificacao sobre os perfis de vento e temperatura.

O proposito do presente trabalho e utilizar um metodo de determinacao de intermitencia e quantificar como esta afeta as series de temperatura e CO 2 . Tais analises sao feitas para um sitio especifico na regiao Amazonica.

Neste trabalho, e analisada a variacao da temperatura atmosferica proximo a superficie considerando quatro diferentes cenarios de concentracao atmosferica de dioxido de carbono. E mostrado que as maiores variabilidades de temperatura ocorrem no estado desconectado na regiao transicao entre os regimes. Os resultados indicam que a diminuicao na variacao de temperatura diurna pode estar associada a variabilidade de regimes na camada limite estavel.

A microburst is a phenomena that occurs in the atmosphere which consist on a very intense downdraft that, after impinging on the ground surface, leads to strongly divergent winds at and just above the ground level. Such winds can reach more than 30 m/s-1 and are associated with high shear forces, representing a serious threat to aircrafts and buildings. The detection and tracking of the front of the microburst expansion at the ground level becomes an important and interesting field for researchers. Previous works show the detection of the vortex core but not for the vortex front. From velocity fields obtained from a LES simulation, we utilize Finite Time Lyapunov Exponents (FTLE) which measures the exponential divergence between particle trajectories. Then we identify manifolds which acts as separatrices of the flow and represent the edge or front of the vortex. By tracking the vortex front we also measure its displacement through time. Find the front of the vortex using only vorticity and velocity fields is complicated and imprecise. Therefore, the combination of these two methods represents a new approach in this particular problem.

Wind power is currently one of the sources of electricity the fastest growing worldwide. However, especially in Brazil, it is still very difficult to locate areas with reliable winds for the implementation of a wind farm, because there is not enough data density that guarante the wind farm efficiency. Thus, the development of models that simulate wind conditions are extremely important for studies and research in this area. In this way, weather reanalysis data can be used as input into high-resolution regional models, for example. Therefore, this work presents a study comparing two sets of weather Reanalysis of wind data - ERA-Interim and CFSR - with measured data from automated weather stations of the National Institute of Meteorology in the Rio Grande do Sul state in order to obtain the coefficient correlation of data from reanalysis with data measured for each measurement point and for every season. For better visualization of the correlation results, it is also built contour maps with correlation coefficient where can be seeing that the best performance of the CFSR reanalysis.

The Southern Brazilian region is specially affected by extreme weather events, very often intense wind gusts coming from deep convection may develop itself as a microburst producing winds higher than 100 km/h. In order to understand the physical and dynamical process evolved in this phenomena, a static and isolated microburst is produced through a Large Eddy Simulation. A quantitative analysis of propagation an maintenance of the microburst vortex ring is performed in order to understand its evolution.

The autocorrelation function of the flow speed components, measures the relationship that the speed in a certain instant, has with the speed at an earlier instant. In some conditions, in the atmospheric flow, this autocorrelation presents a low frequency oscillatory shape, presenting negative lobes. This behavior is known as meandering phenomenon and becomes prevalent in low wind conditions. The objective of this study is to compare the adjustments of autocorrelation functions, present in the literature, with trial of the experimental data of FLOOSS II experiment, for determining the meandering oscillation period. Initially, three selection criteria were used to select the windows of analysis. Among the criteria the magnitude of the wind showed the most satisfactory. The fitting curves showed that both autocorrelation functions performed well, even with a large variability of oscillation periods that were found. The great variability in the oscillation period of the meandering phenomena can be associated with the nature of the physical phenomenon that is responsible for its origin. However, this hypothesis needs confirmation.