Abstract
Wake flow behind a permeable disk is visualized, which phenomenologically simulates far-wake aerodynamic characteristics of a horizontal axis wind turbine. Smoke wire method and hot wire anemometer are used to evaluate periodic fluctuation of the flow in the region from 5 to 25 times the disk diameter downstream to the permeable disk. The experiment has shown that there causes a significant three-dimensional spiral-like vortical fluctuation that long persists downstream within the wake. Decrease in solidity of the permeable disk, thus, increase in aerodynamic permeability of the wind turbine, lowers Strouhal number for primary frequency of the velocity fluctuation and decreases the time averaged velocity and turbulence intensity of wake behind the disk.
