An investigation into the potential for wind turbines to cause barotrauma in bats
Fig 2
Smoke visualization of a blade-tip vortex at the national aeronautics and space administration’s ames research center 40-by-80-ft wind tunnel.
The visible helical vortex indicates the region of low pressure caused by the blade-tip vortex. Note that this visualization was performed under low-turbulence conditions in a wind tunnel, allowing the vortex to advect downwind with the mean flow with its helical structure intact. In the atmosphere, where the turbulence intensity is typically much higher, the vortex structure is commonly unrecognizable within one rotor diameter downstream of the rotor plane. Photo by Lee Jay Fingersh, National Renewable Energy Laboratory, 55062.