Abstract
In this work, we investigated the flow structure around actuator arms with and without a weight-saving hole, and clarified the unsteady flow in detail. We found that a three-dimensional spiral vortex in the wake region of the arm and the flow spilled from the weight-saving hole. These flows can be considered to be an excitation source for the actuator arm. The power spectrum of the arm torque generated by calculated wind disturbance agrees with that of measured wind disturbance. This verifies the existence of the calculated vortices and the flow spilled from the weight-saving hole.
