Neighbors of turbine farms often complain about the noise they make. Now a Virginia Tech team of researchers has come up with a way they say will dampen that sound.
Opponents of wind farms often claim the noise is a nuisance and disturbs residents living in close proximity to the machines. As the blades slice through the air, the sharp edge at the back converts the air’s turbulence into sound waves, creating what’s called a trailing edge noise. Researchers have already determined the wings of certain species of owls who fly almost silently have a flexible and porous trailing edge. William Devenport, professor of aerospace and ocean engineering at Virginia Tech, teamed up with colleagues from around the country who studied the soft down and tiny hairs growing out of the wings’ surface. They duplicated them to see what effect that might have on reducing noise.
“We really took inspiration from the owl’s hairs and applied it to the wind turbine blade model and adapted it to configurations that were practical and then found we had substantial noise reduction.”
They discovered the hairs actually form a canopy above the wing but they couldn’t replicate the canopy in Tech’s wind tunnel. So Devenport says doctoral student Ian Clark improvised.
“Ian went down to the fabric store and found some wedding veil fabric that behaved like a canopy; that behaved like a canopy; that looked like it had the same open area ratio as the owl down.”
He found it reduced the wind pressure by 1,000 times. Then they created more than 20 different configurations of small fins and put them on the turbine blades and nearly all of them reduced the noise level.
“Another step for us is to embark on work where we try to understand at a fundamental level what these are actually doing.”
Devenport says the next obvious step would be to partner with a turbine manufacturer to develop something to place on the blades.