In 1995 the conundrum of bumblebee flight got its final solution. And this week the aerodynamics of a hovering bat species has been revealed. Its flight was studied in the wind tunnel laboratory of Lund University, and the results are published in the prestigious journal Science.
The wind tunnel at Lund University is specially crafted for research on bird flight. Birds fly “at the spot” against a headwind, allowing detailed investigation of wing movements using high speed video cameras. It’s also possible to visualize the vortices around the wings and in the wake using fog as tracer particles.
In 2003 professor Anders Hedenström investigated the aerodynamics of bird flight using this method for the first time. In the spring 2007 his lab presented results from applying this method to flying bats for the first time. A nectar-feeding bat species, Palla’s long-tongued bat, was trained to visit a feeder in the wind tunnel. By varying the speed between 0 m/s (hovering) to 7 m/s, different behaviors were studied.
"When we investigated the aerodynamics of our bats we discovered that the wings generated more lift than they should at the slowest speeds (as dictated by classic wing theory),"says professor Hedenström.
"We recorded vortices shed in the wake, which we know well from our previous studies on birds. Now, our new study show that a stable leading edge vortex (LEV) is developed on top of the wing, and this vortex adds significant amounts of lift. Such vortices were previously known in insects, for example in bumblebees, and it was the discovery of leading edge vortices that finally resolved the bumblebee flight conundrum."
How can the bats generate such high lift? One of the team members and lead author of the new study, Florian Muijres, explains:
"The high lift arises because the bats can actively change the shape (curvature) by their elongated fingers and by muscle fibers in their membranous wing. A bumblebee cannot do this; its wings are stiff. This is compensated for by the wing-beat frequency. Bats beat their wings up to 17 times per second while the bumblebee can approach 200 wing-beats per second."
The paper in Science is: Leading-Edge Vortex Improves Lift in Slow-Flying Bats, authors are F T Muijres, L C Johansson, R Barfield, M Wolf, G R Spedding and A Hedenström.Image legends:
Ingela Björck | alfa
Scientists spin artificial silk from whey protein
24.01.2017 | Deutsches Elektronen-Synchrotron DESY
Choreographing the microRNA-target dance
24.01.2017 | UT Southwestern Medical Center
A Swedish-German team of researchers has cleared up a key process for the artificial production of silk. With the help of the intense X-rays from DESY's...
For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.
According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
24.01.2017 | Physics and Astronomy
24.01.2017 | Life Sciences
24.01.2017 | Health and Medicine