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
What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering