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The objective of this paper is to characterize the wake flow from a high-solidity propeller four-blade horizontal axis rotor commonly used in hydrokinetic turbines. A numerical and experimental study was conducted to describe the turbulent flow in the wake. Velocity flow measurements were obtained using PIV and hot-wire anemometry techniques in two different wind tunnel facilities. CFD simulations were carried out using a 3D full description of the rotating turbine rotor with an unsteady model. Additionally, simulations were conducted using a simplified model that described the rotor as actuator lines. The numerical results and experimental data were compared, and the study achieved good results for estimating machine performance and describing the main vortex structures in the turbine wake.

The aim of the present paper is to discuss the monitoring strategies for a modular hydrokinetic turbine system. A floating triangular-frame arrangement of three propeller hydrokinetic turbines is installed in the outflow channel of a hydropower plant, in the interest of remaining water stream energy conversion. The monitoring techniques based on Wireless Sensor Networks (WSN) and the Internet of Things (IoT) are reported, taking into account the specific framework of the instrumentation and data management in field experiments.

In the present paper, wind tunnel experiments with horizontal axis propeller hydrokinetic turbine models are carried out. The turbine performance is assessed for different diffuser configurations and operational ranges. The present experiments evaluate the use of two different geometries of rear diffusers to enhance the power output of the free flow machine. The present paper reports an increase of the power coefficient of about 48 % –79 % . A discussion about the use of the diffuser technology is pointed out in a framework of a concept of the minimization of the volume of material contained in the turbine parts. It represents an important result that has to be taken into account in the design of hydrokinetic turbines.

In this work, we proposed an upscaling methodology to extrapolate results from wind tunnel experiments with small-scale model to the full-size hydrokinetic turbine. Small-scale 1:20 wind tunnel experiments ( $${\hbox {Re}}\sim 10^4$$ ), with a three-blade horizontal axis turbine, were carried out looking to identify the characteristic curves of a full-size turbine operating in water ( $${\hbox {Re}}\sim 10^6$$ ). The lack of dynamic similarity due to unmatched Reynolds numbers is analyzed in the framework of blade element momentum theory arguments. A new semi-empirical power-law equation is achieved, uniquely based on the BEM theory which relates the power coefficients of model and full-size turbine to the Reynolds numbers and a power factor, specific to each turbine. Computational fluid dynamic CFD simulations for the same rotor geometry, simulating different runners with varying diameters from small-scale model to full-scale turbine are carried out to validate the upscaling arguments, and to verify the accuracy of the power coefficient curves predicted by proposed methodology.

International audience; A design study of propeller hydrokinetic turbines is explored in the present paper, where the optimized blade geometry isdetermined by the classical Glauert theory applicable to the design of axial flow turbines (hydrokinetic and wind turbines).The aim of the present study is to evaluate the optimized geometry for propeller hydrokinetic turbines, observing the effectof the number of blades in the runner design. The performance of runners with different number of blades is evaluated in aspecific low-rotational-speed operating conditions, using blade element momentum theory (BEMT) simulations, confirmedby measurements in wind tunnel experiments for small-scale turbine models. The optimum design values of the power coefficient,in the operating tip speed ratio, for two-, three- and four-blade runners are pointed out, defining the best configurationfor a propeller 10 kW hydrokinetic machine.

International audience; A design study of propeller hydrokinetic turbines is presented. The main objective is to evaluate the optimized geometry forhorizontal axis hydrokinetic turbines, take into account the runner design with a different number of blades. The optimized bladegeometry is determined by the Glauert theory for axial free flow turbines (hydrokinetic and wind turbines). The performance ofthe different blades is evaluated in the entire range of operating conditions, using Blade Element Momentum Theory (BEMT).Computational Fluid Dynamics (CFD) computations were also carried out to evaluate the detailed features of the fluid flow

This study aims to obtain wake information, which passes through a linear array of turbines. Is presented a numerical approach to observe what effect can be obtained from a 2.2 meters turbines set. The linear array parameters were based on the Hydro-k project, in which two unconfined in-line rotors were used. The studies were performed by analyzing three variables: mean normalized velocity, turbulence kinetic energy and turbulence intensity. It was noted that the iteration between the rotors alters the flow on the array of turbines increasing the center speed.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2015. O principal objetivo deste trabalho é investigar o comportamento do fator de indução axial, ao longo do escoamento de uma turbina de eixo horizontal, utilizando a teoria clássica de aerodinâmica de rotores e simulações numéricas do tipo RANS com o modelo de turbulência SST. O estudo foi realizado para uma turbina eólica de 500W. As simulações foram validadas utilizando dados experimentais do coeficiente de potência (Cp) obtidos em ensaios em túnel de vento aberto. Foi observado que fator de indução não é uma variável integral do escoamento, sendo ele uma função das coordenadas espaciais do sistema. Assumiu-se uma equação linear como modelo o fator de indução em cada plano a montante da turbina. Uma curva do coeficiente de potência máximo para essa turbina foi calculada aplicando o modelo do fator de indução proposto e teoria de Glauert para máximo valor de Cp. Por meio dessa curva, foi introduzido o conceito de velocidade de ponta de pá crítica, sendo descrita como uma condição operacional em que existe um ponto de operação que a turbina está girando sem nenhuma potência. The main objective of this work is to investigate the axial induction factor behavior, along the flow of a horizontal axis turbine, using the classical theory of aerodynamics rotors and numerical simulations RANS and turbulence model SST. The study was conducted for a 500W wind turbine . The simulations were validated using experimental data of power coefficient that was obtained in open wind tunnel tests. It was observed that induction factor is not an integral flow variable, it is a space coordinates function . It was assumed a linear equation to model the induction factor in each plane upstream of the turbine. A curve of the maximum power coefficient, for this turbine, was calculated by applying the induction factor model proposed and Glauert theory to Cp maximum . By this curve, it was introduced the concept of critical tip speed ratio, which is described as an operating condition point that there is some rotation, but the power coefficient is null.