Solar chimney is nowadays an important source of renewable energy, especially in the hot region of the world. In this paper, the solar chimney is investigated based on the ambient conditions of Tunisia. An experimental setup is developed to study the solar chimney under the Tunisia weather conditions. Numerous simulations are performed to study the chimney diameter effect. The airflow characteristics are analyzed for the different chimney diameters. The depression zone in the chimney inlet increases with the increase of the chimney diameter. Consequently, the velocity value increases. The comparison between the numerical and the experimental results shows a good agreement.