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 investigating 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.