Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Investigating the effect of geometrical parameters of an optimized wind turbine blade in turbulent flow M. Tahani a, ⁎ , T. Maeda b , N. Babayan a , S. Mehrnia a , M. Shadmehri a , Q. Li b , R. Fahimi a , M. Masdari a a Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran b Division of Mechanical Engineering, Mie University, Tsu, Japan ARTICLE INFO Keywords: Horizontal axis wind turbine Turbulence Optimization Ant Colony CFD ABSTRACT The geometry of a wind turbine must always be optimized in order to capture the maximum amount of available power. The main geometrical parameters of a wind turbine are chord and twist distributions and also airfoils at different sections. In this research study it is aimed to optimize the geometry of a wind turbine and also in- vestigating the influence of geometrical parameters on the performance of the turbine in 1% and 8% turbulence intensities. For this purpose, first a blade element momentum theory code has been developed and has been validated using available experimental data. Then, six chord distribution functions, ten twist distribution functions and also 12 airfoils are considered in order to obtain the optimum geometry. According to the discrete nature of the problem, popular ant colony optimization algorithm has been utilized. After obtaining the optimum design, computational fluid dynamics has been utilized for studying the physics of the flow. The results indicated that by increasing turbulence intensity, the wake recovery gets faster because of increasing the wake turbulent kinetic energy. And also it was shown that for the optimized geometry the flow separation is delayed therefore more power production can be achieved. 1. Introduction Nowadays, countries of the world are facing with a common pro- blem, called, energy. Fossil fuels restrictions, air pollution and etc. has directed the attention of all governments to renewable energy sources. Utilization of some renewable energy sources, such as wind energy has a historical background. Wind energy is one of the promising markets which has experienced a significant growth in recent years. Although its popularity, lack of knowledge in some fields has restricted its applica- tion. For example, the influence of turbulence intensity on the perfor- mance of wind turbines is an incomplete field of knowledge, which requires more attention. Turbulence intensity, directly affects the tur- bine performance and also its structural design, therefore study in this field is in priority. Several research studies have been carried out in this field which some of them are presented here. In the experimental study carried out by Li et al. [1], the effect of three different turbulence intensities (TI = 1.4%, 8% and 13.5%) has been investigated on the power performance of a two bladed horizontal axis wind turbine. According to the results, the power coefficient strongly depends on pitch and yaw angles. In another study carried out by Li et al. [2], the wake characteristics of a horizontal axis wind turbine has been investigated using wind tunnel in different turbulence intensities. According to the presented results, by increasing the tur- bulence intensity, the wake area decreases and wind speed recovery occurs faster. Effect of turbulence intensity in yawed and no-yawed condition was investigated by Li et al. [3]. In this research study, it was indicated that extremely low turbulence intensity decreases the power coefficient and at low tip speed ratios, 30-degree yaw angle would in- crease the power coefficient. The application of four different turbu- lence models in predicting the power performance of the turbine was investigated by Tahani et al. [4]. − k ωSST , − v f 2 , − k εRNG and Spalart- Allmaras one equation were selected models. According to the pre- sented results, the predicted output power by − k εRNG and − v f 2 were more accurate. In the research carried out by Cai et al. [5], unsteady simulation of horizontal axis wind turbine has been carried out using CFD. In this research study, the simulation has been conducted by considering the wind shear, tower shadow and yaw motion. The results indicated that the maximum aerodynamic loads are generated at the upwind azimuth during yaw motion. Nedjari et al. [6], investigated the wind turbines wake characteristics in a complex topography using nu- merical methods. In this research study the soil effects on the wake are considered by means of the size length of the eddy areas of low speed http://dx.doi.org/10.1016/j.enconman.2017.09.073 Received 11 June 2017; Received in revised form 27 September 2017; Accepted 28 September 2017 ⁎ Corresponding author. E-mail address: m.tahani@ut.ac.ir (M. Tahani). Energy Conversion and Management 153 (2017) 71–82 0196-8904/ © 2017 Elsevier Ltd. All rights reserved. MARK