2016 年 82 巻 839 号 p. 16-00023
This study deals with the time-mean aerodynamic characteristics of a concentrator photovoltaic system (CPV), which is mainly composed of a rectangular panel and a cylindrical shaft. It consists of wind tunnel and water tank experiments. Attention was focused on the effects peculiar to the flow around the CPV. First, placing a scale model in a wind tunnel, we made measurements on its aerodynamic characteristics for different incidence angles φ and yaw angles θ of the panel relative to the direction of the oncoming flow. The aerodynamic characteristics were examined for the case with the panel settled vertically, i.e., φ is set to 0°, but θ is varied. The results are fairly close to those of a single square plate by other investigators. For non-zero values of φ, however, the differences of the aerodynamic forces are perceived between two cases taking two attitudes for which each other is mirror images. The distribution of the differences is displayed on the φ-θ plane. Here, the corresponding cases where the acceptance surface faces upstream and downstream are called ‘upstream-facing case’, and ‘downstream-facing case’ respectively. This analysis clearly shows a trough showing more pressure recovery for the upstream-facing case. Next, to make clear the cause of the pressure recovery, we performed flow visualization in a water channel, where fluorescein dye was injected into the near-wake regions of the model. The flow visualization indicates that the pressure recovery is probably due to a difference between upstream- and downstream-facing cases in development of the shear layer separated from the side with a larger separation angle . The upper separated shear layer rolls up freely for the downstream-facing case, but the growth of the lower one is inhibited by the ground for the upstream-facing case.
