Date: October 19, 2018
Source: Lund University
For the first time, researchers have measured what is known as the ground effect of flying animals -- and it turns out that they save a lot more energy by flying close to the ground than previously believed. The study from Lund University in Sweden supports one of the theories on how birds began to fly.
"Our measurements show that the ground effect saves animals twice as much energy as models have suggested.," says Christoffer Johansson, biologist at Lund University.
For the first time, Christoffer Johansson, together with colleagues Anders Hedenström at Lund University and Lasse Jakobsen at the University of Southern Denmark, have successfully managed to measure the ground effect when Daubenton's bats fly in a wind tunnel.
In short, the ground effect means that a surface, ground or water, acts as an aerodynamic mirror that increases the air pressure under the wings -- it costs less to generate lift. The ground effect is achieved within one wingspan of the surface, and the effect decreases exponentially with distance to the surface. An even surface, e.g. a calm lake where bats and birds catch insects or drink while they fly, provides optimal conditions. The new study also shows that animals use even less energy if they flap their wings rather than gliding near the ground.