The present study aims to numerically determine the geometric proportions that maximize the performance of a Savonius rotor with a split Bach blade profile. For this, the response surface methodology was used through a full factorial experimental design, comprised of four factors corresponding to the width (C) and length (L) of the overlap, and the eccentricity (E) and radius (R) of the blade, which define the geometry of the rotor. The models built from the different treatments of the experimental designs were analyzed using computational simulations in order to obtain the power coefficient ($C_P$), considered as the response variable. The same parameters and models of computational fluid dynamics were used to analyze each geometry through the ANSYS Fluent software. The analysis of the obtained results showed that there is a great interaction among the evaluated factors, which demonstrates the importance of analyzing them together. The results obtained with the full factorial experiment design were compared with those obtained from a face-centered central composite design, evidencing a difference of only 0.30% in the estimate of the regression model. A $C_P$ of 0.2661 was obtained from the optimized geometry, which represents a 36.50% increase in its performance with respect to the conventional semicircular profile. The optimal dimensions obtained are 4.69, 21.45, 5.52 and 25.15 in percentage values of the rotor diameter, for parameters C, L, E and R parameters, respectively. Experimental data available in the literature were used to contrast the numerical results and a good fit was revealed.

In the present study, the implementation of multi-blade profiles in a Savonius rotor was evaluated in order to increase the pressure in the blade’s intrados and, thus, decrease motion resistance. The geometric proportions of the secondary element were determined, which maximized the rotor’s performance. For this, the response surface methodology was used through a full factorial experimental design and a face-centered central composite design, consisting of three factors, each with three levels. The response variable that was sought to be maximized was the power coefficient ($C_P$), which was obtained through the numerical simulation of the geometric configurations resulting from the different treatments. All geometries were studied under the same parameters and computational fluid dynamics models through the ANSYS Fluent software. The results obtained through both experimental designs showed a difference of only 1.06% in the performance estimates using the regression model and 3.41% when simulating the optimal proportions geometries. The optimized geometry was characterized by a $C_P$ of 0.2948, which constitutes an increase of 10.8% in its performance compared to the profile without secondary elements and of 51.2% compared to the conventional semicircular profile. The numerical results were contrasted with experimental data obtained using a wind tunnel, revealing a good degree of fit.

Contexto: Las turbinas eólicas de eje vertical, y en particular las turbinas de arrastre tipo Savonius, aventajan a los otros tipos de turbinas en aplicaciones que comprenden vientos erráticos y de baja velocidad. Si bien su eficiencia está entre las más bajas, esto puede verse compensado con sus bajos costos, lo que las convierte en una alternativa sostenible y atractiva para este tipo de aplicaciones. En esta investigación se busca seleccionar la geometría de mayor rendimiento para el álabe de una turbina eólica tipo Savonius. Método: Para ello, se analizan numéricamente diversas configuraciones geométricas empleadas en este tipo de turbinas, las cuales fueron consultadas en la literatura. Todos los modelos de perfil son estudiados bajo los mismos parámetros y modelos de dinámica de fluidos computacional a través del software ANSYS Fluent. Resultados: A través de las simulaciones computacionales se estiman las condiciones de optimo rendimiento de cada una de las geometrías. Dichas condiciones permiten comparar, bajo los mismos términos, el desempeño de los perfiles e identificar los de mayor rendimiento. Se determina que el perfil semicircular convencional y el conocido como Bach modificado presentan coeficientes de potencia de 0,287 y 0,395 respectivamente, lo que representa un aumento en su rendimiento del 37,8 %. Conclusiones: Este resultado superior motiva a un análisis detallado del perfil Bach modificado que permita encontrar las proporciones geométricas óptimas para su desempeño aerodinámico. Context: Vertical-axis wind turbines, and Savonius-type turbines in particular, outstrip other types of turbines in applications that include erratic and low-speed winds. Although their efficiency is among the lowest, this can be compensated by their low cost, turning them into a sustainable alternative which is also appealing for this type of applications. This research seeks to select the highest-performance geometry for the blade of a Savonius-type wind turbine. Method: To this effect, various geometric configurations used in this type of turbines, which were consulted in the literature, are numerically analyzed. All the profile models are studied under the same computational fluid dynamics parameters and models through the ANSYS Fluent software. Results: Through computational simulations, the optimal performance conditions of each of the geometries are estimated. These conditions allow comparing the performance of the profiles under the same terms, as well as identifying the ones with the highest performance. It is determined that the conventional semicircular profile and the one known as the modified Bach have power coefficients of 0,287 and 0,395, respectively, which represents a performance increase of 37,8%. Conclusions: These superior results motivate a detailed analysis of the modified Bach profile which allows finding the optimal geometric proportions for its aerodynamic performance.

Contexto: Este estudio evalúa la estabilidad estructural de un rotor tipo Savonius implementando un perfil multielemento, con el propósito de reducir la resistencia al movimiento y mejorar así el rendimiento aerodinámico. El rotor con el perfil en estudio se comparó con rotores de perfiles semicircular convencional y Bach dividido. Método: Se analizó la interacción fluido-estructura mediante la simulación numérica de los tres rotores, y se determinó el estado de esfuerzos y deformaciones en un régimen normal de operación. A los rotores se les asignó el mismo material de construcción, y estos fueron estudiados bajo los mismos parámetros y modelos de la dinámica de fluidos y mecánica computacional a través del software ANSYS. Resultados: Los resultados obtenidos evidenciaron un mejor comportamiento estructural en el rotor con la configuración multielemento, al reducir el esfuerzo equivalente máximo en 59,10 y 42,87\% y las deformaciones en 47,40 y 33,59\% con respecto a los rotores de perfiles semicircular convencional y Bach dividido respectivamente. Conclusiones: La configuración multielemento permite un mayor rendimiento aerodinámico y estructural, a la vez que se conserva la simplicidad de construcción y operacional que caracterizan al rotor tipo Savonius.