Mesh motion methods for numerical aerodynamic design of lift and control surfaces

In this work, moving mesh methods based on the solution of pseudo structural and fluid problems are developed. Mesh motion methods are necessary features for numerical aerodynamic design and test of lift and control surfaces of UAVs. Here a particular moving mesh method based on a pseudo Stokes problem is compared to different well known moving mesh approaches such as techniques by solving diffusion and pseudo structural problems with prescribed velocity and displacement fields, respectively. The benchmark test for this comparison is an airfoil with a fully meshed domain, including the far field and boundary layer, over which is imposed a rotation velocity boundary condition. In order to distinguish the mesh motion methods, several mesh quality criteria are employed to determine a mesh quality mapping to identify critical regions with poor mesh quality and to access the performance of each mesh motion approach. In order to illustrate the mesh motion technology, this paper also presents results of the numerical simulation of a laminar flow over a NACA 0012 airfoil by using a numerical code based on a finite element projection method augmented with mesh motion capabilities

On the design of propeller hydrokinetic turbines: the effect of the number of blades

A design study of propeller hydrokinetic turbines is explored in the present paper, where the optimized blade geometry is determined 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 effect of the number of blades in the runner design. The performance of runners with different number of blades is evaluated in a specific low-rotational-speed operating conditions, using blade element momentum theory (BEMT) simulations, confirmed by 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 configuration for a propeller 10 kW hydrokinetic machine

AVALIAÇÃO DE POTENCIAL HIDROCINÉTICO REMANESCENTE A JUSANTE DE UHES NA BACIA HIDROGRÁFICA DO RIO TIETÊ

A modelagem hidrodinâmica fluvial tem sido amplamente utilizada como uma ferramenta computacional para estimar o potencial hidrocinético de reservatórios de jusante de UHEs, ou seja, aproveitando a energia remanescente. O presente estudo avaliou o potencial de duas UHEs localizadas na bacia hidrográfica do rio Tietê, as UHEs de Ibitinga e Bariri, buscando demonstrar qual das duas possui maiores velocidades em seu reservatório de jusante, já que a velocidade varia ao cubo quando se está interessado em maiores potenciais hidrocinéticos. O escoamento foi simulado através do modelo Saint-Venant. Para tanto, foram levantados dados de topobatimetria para a elaboração do modelo de elevação do terreno; dados de substrato para obtenção do coeficiente de Manning, e dados de vazão e nível d’água para as condições de contorno. O modelo para as duas UHES foram validados e calibrados com dados observados de profundidade e velocidade. A partir desse modelo, velocidades e profundidades dos dois reservatórios de jusante foram simuladas para as vazões máxima, média, mínima observadas no período de 2010 a 2014. Os resultados de velocidade apontam um maior potencial hidrocinético para UHE Ibitinga, pois suas velocidades máximas, para as vazões simuladas variam entre 1,468m/s (vazão mínima) e 2,703 m/s (vazão máxima). Enquanto que as velocidades para UHE Bariri variam entre 0,61m/s e 2,05m/s

English

A design study of propeller hydrokinetic turbines is presented. The main objective is to evaluate the optimized geometry for horizontal axis hydrokinetic turbines, take into account the runner design with a different number of blades. The optimized blade geometry is determined by the Glauert theory for axial free flow turbines (hydrokinetic and wind turbines). The performance of the 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 flo

Numerical Study of Wake Characteristics in a Horizontal-Axis Hydrokinetic Turbine

Over the years most studies on wake characteristics have been devoted to wind turbines, while few works are related to hydrokinetic turbines. Among studies applied to rivers, depth and width are important parameters for a suitable design. In this work, a numerical study of the wake in a horizontal-axis hydrokinetic turbine is performed, where the main objective is an investigation on the wake structure, which can be a constraining factor in rivers. The present paper uses the Reynolds Averaged Navier Stokes (RANS) flow simulation technique, in which the Shear-Stress Transport (SST) turbulent model is considered, in order to simulate a free hydrokinetic runner in a typical river flow. The NREL-PHASE VI wind turbine was used to validate the numerical approach. Simulations for a 3-bladed axial hydrokinetic turbine with 10 m diameter were carried out, depicting the expanded helical behavior of the wake. The axial velocity, in this case, is fully recovered at 12 diameters downstream in the wake. The results are compared with others available in the literature and also a study of the turbulence kinetic energy and mean axial velocity is presented so as to assess the influence of proximity of river surface from rotor in the wake geometry. Hence, even for a single turbine facility it is still necessary to consider the propagation of the wake over the spatial domain

COMPARACAO DE METODOLOGIAS CFD DE SIMULACAO DE TURBINAS HIDROCINETICAS

The recent advances in technologies turned able that a computer provides a numerical simulation of fluid flows, well known as Computational Fluid Dynamics (CFD) technique. It means that the physical laws that govern the fluid behavior is in a “virtual” environment, where we can visualise the whole prototype system, such as a turbine, and how it works with great levels of realism. For many reasons, such as turbulence level and computational resource available, it is often impossible to describe the entire system with its all details. Consequently,we simplify the problem as much as possible to achieve the solution. In this sense, the aim of this work is to assess two different methodologies of CFD simulations of a 3 blade hydrokinetic turbine: full rotor and just one blade with symmetry simplification. As a result of it, the simulation of one blade rotor showed similar values of torque and pressure coefficient with the full rotor case.Thereby, this simplification presented the same level of results with a third of mesh

AVALIAÇÃO DE POTENCIAL HIDROCINÉTICO REMANESCENTE A JUSANTE DE UHES NA BACIA HIDROGRÁFICA DO RIO TIETÊ

A modelagem hidrodinâmica fluvial tem sido amplamente utilizada como uma ferramenta computacional para estimar o potencial hidrocinético de reservatórios de jusante de UHEs, ou seja, aproveitando a energia remanescente. O presente estudo avaliou o potencial de duas UHEs localizadas na bacia hidrográfica do rio Tietê, as UHEs de Ibitinga e Bariri, buscando demonstrar qual das duas possui maiores velocidades em seu reservatório de jusante, já que a velocidade varia ao cubo quando se está interessado em maiores potenciais hidrocinéticos. O escoamento foi simulado através do modelo Saint-Venant. Para tanto, foram levantados dados de topobatimetria para a elaboração do modelo de elevação do terreno; dados de substrato para obtenção do coeficiente de Manning, e dados de vazão e nível d’água para as condições de contorno. O modelo para as duas UHES foram validados e calibrados com dados observados de profundidade e velocidade. A partir desse modelo, velocidades e profundidades dos dois reservatórios de jusante foram simuladas para as vazões máxima, média, mínima observadas no período de 2010 a 2014. Os resultados de velocidade apontam um maior potencial hidrocinético para UHE Ibitinga, pois suas velocidades máximas, para as vazões simuladas variam entre 1,468m/s (vazão mínima) e 2,703 m/s (vazão máxima). Enquanto que as velocidades para UHE Bariri variam entre 0,61m/s e 2,05m/s