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Venus Flytrap inspires new aircraft flap design

18 August 2015

Researchers at the German Aerospace Centre (DLR) are developing a morphing wing trailing edge that smoothly transforms into any shape.

The Venus Flytrap (image: Shutterstock)

The flaps on the wings of today’s commercial airliners are actuated via a complicated mechanism. Their arrangement and the resulting gap when they are extended compromises the aerodynamics, increases fuel consumption and contributes to in-flight noise.

The new technology is flexible, its movement being based on that of carnivorous plants, enabling the gap between the wing and the flap to be eliminated. The Venus Flytrap proved to be a good source of inspiration.

“The carnivorous Dionaea Muscipula needs to be able to close its trapping leaves very quickly to catch its flying insect prey,” says Benjamin Gramüller from the DLR Institute of Composite Structures and Adaptive Systems. “It does this by changing the pressure in the leaf cells and using a leaf-shape geometry optimised through evolution.”

Research has shown that the Venus Flytrap builds up tension through water pressure. When triggered – when a fly enters the trap – this can be quickly discharged. The trap then snaps shut. “We are now using the principle behind the plant’s movement for aeronautics applications,” adds Gramüller.

The DLR researcher and his colleagues have translated the cell system’s method of using pressure to assume a desired shape on the trailing edge of a wing. To do so, they have developed a 'flap demonstrator', which is operated with compressed air and can flexibly assume aerodynamic shapes for cruising or landing.

The plastic cells in the demonstrator have different sizes to form the appropriate shape for the trailing edge of the wing. Two layers of cells lie one on top of the other.

“To raise the edge, we pressurise the lower cell layer, and to lower it, we pressurise the upper one,” explains Gramüller. “The compressed air can be easily supplied from the existing compressed air system in an aircraft.”

DLR's flap demonstrator

The researchers have been able to use the new flight technology to demonstrate that the desired flap shapes for take-off and landing can be achieved, depending on how the compressed air is applied.

The PACS (Pressure Actuated Cellular Structures) research project is being carried out in conjunction with Airbus Defence and Space.

Folding 'snap' geometry'

Also inspired by the natural 'snapping' action of the Venus Flytrap, physicist Christian Santangelo at the University of Massachusetts Amherst has developed a way to use curved creases to give thin curved shells a fast, programmable snapping motion. The new technique avoids the need for complicated materials and fabrication methods when creating structures with fast dynamics.

The advance should help materials scientists and engineers who wish to design structures that can rapidly switch shape and properties, says Santangelo. He and colleagues, including polymer scientist Ryan Hayward, point out that until now, there has not been a general geometric design rule for creating a snap between stable states of arbitrarily curved surfaces.

"A lot of plants and animals take advantage of elasticity to move rapidly, yet we haven't really known how to use this in artificial devices," says Santangelo. "This gives us a way of using geometry to design ultra-fast, mechanical switches that can be used, for example, in robots." 

Details of the new geometry appear in an early online issue of Proceedings of the National Academy of Sciences.

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