01. Experimental/Computational Fluid Dynamics

The development of electricity generation methods using sustainable energy is progressing, and wind power is featured as one of these methods. However, large propeller wind turbines must be built in locations away from residential areas, from the point of view of the landscape and noise. On the other hand, a Magnus wind turbine is expected to be installed in urban areas because it is compact and operates quietly. Therefore, the cost of electricity transmission can be reduced compared to large propeller wind turbines. A Magnus wind turbine is a wind turbine system that uses rotating cylinders instead of the traditional propeller-type blades. When the cylinders rotate, the lift is generated by using the Magnus effect. In the previous study, it was confirmed that the lift force was enhanced by attaching fins to the cylinder. However, the details of flow fields around the rotating cylinder due to the interaction between the fins and a freestream have not been fully understood. The effect of fin shape on lift generation can be clarified by investigating the relationship between lift variations and unsteady flow fields during rotation. In the present study, time-dependent particle image velocimetry (PIV) was carried out to measure the unsteady flow fields for several types of fins attached to the cylinder in wind tunnel tests at the Institute of Fluid Science, Tohoku University. The vortex was generated by the interaction of the fins with the freestream, and this vortex becomes strong as the cylinder rotates. After that time, the vortex sheds from the fin tip, and the lift force variations during one rotational cycle are related to the behavior of this vortex. In order to increase lift, it is important for the strong vortex to exist near the cylinder surface.