It’s the grand vision of engineers: maximum fuel efficiency in airplanes, automobiles and railway trains thanks to nearly turbulence-free surface currents. But that will require a great deal of basic research with today’s very time- and work-intensive research methods. Gabriel Axtmann of the University of Stuttgart’s Institute of Aerodynamics and Gas Dynamics (IAG) is working on a solution that would not only simplify current measurements but would also be easy to use. The doctoral candidate’s secret is nature itself, more precisely: the lowly cricket.
The cricket uses fine hairs on its nether body appendages to perceive and interpret acoustic waves from its surroundings. It’s a matter of survival: depending on the direction in which pressure waves bend the sensorial hairs, the cricket can estimate, for example, how groß and dangerous a coming object is. This is the principle used by Gabriel Axtmann for his research work.
With the aid of a computer sensory reactions are visible
The basic idea can be illustrated by an aircraft wing. The researcher’s interest is on the threshold at which a laminar current becomes turbulent . The first major step is to make this ‘point of transition’ visible and to interpret it. Engineer Axtmann conducted all of his experiments at the computer - a big advantage over time-consuming current measurement methods like ‘particle image velocimetry’ (PIV). In Axtmann’s research design, the hairs show up in the form of a mathematical grid matrix, which he then subjects virtually to eddying currents. Depending on the form, speed and dissemination of the eddies, the hairs bend in a specific manner. That is, their sensory reactions reflect the current event.
The algorithms programmed in this manner are able to recognize differences in current and thus determine the ‘point of transition’. The young researcher’s next step is then to study possible laminar wing designs. His idea is that the hairs are not merely reactive, but also proactive, that is, they affect the current depending on whether, for example, they are more rigid or more vibrational in design. They can then give back an impulse that charges the current with energy and makes it remain longer on the surface. As a result the ‘point of transition’ shifts its position. When applied practically, this could mean that a sort of ‘hair toupee’ would be glued at pre-defined points to aircraft wings and would then modify air currents, making the wing much more fuel-efficient. The idea could also be applied to railway trains, automobiles, fans, stationary gas turbines, and wind energy plants. All these applications would then be a product of nature – modelled on the lowly cricket. Linny Bieber
What is Bionics?
Bionics deals with the creative transfer of natural phenomena to technology. The idea behind this interdisciplinary field of research is that life as found in nature has worked out structures, processes and solutions through evolution which man can use systematically for applications involving technical objects and methods. Bionics also plays an important role in many research areas at the University of Stuttgart.