As fast as a shark in water

Dec 15, 2006

With the help of tiny ridge-like structures in their scales, sharks are able to minimize drag when swimming. A new coating system takes advantage of this “riblet effect” to improve the aerodynamics of vehicles and aircraft.

Scales have a beneficial effect on the speed at which fish swim: tiny ridges arranged parallel to the swimming direction, known as “riblets”, reduce drag in water. This riblet effect, which has been known to scientists and engineers for more than 50 years, can also be utilized by ships and other means of transport: Films with a suitable structure can be applied to their outer surfaces to reduce frictional resistance and thus bring down fuel consumption.

The problem is that these films can only be applied to flat or convex surfaces, but bodies whose aerodynamic or hydrodynamic properties have been optimized tend to have a more complex shape. The alternative to coating with a film is to texture the surface itself with riblets. However, none of the laser or milling techniques which have been employed so far are suitable for components that have to be painted, as the paint would immediately flow into the tiny grooves and fill them.

Dr. Volkmar Stenzel of the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research IFAM (Germany) thus came up with the idea of integrating the riblet pattern into the lacquer itself. “That meant we had to look for a tool which didn’t adhere to the lacquer, so that it could impress the required structure onto it,” explains Stenzel. A prototype has now been created, combining a suitable lacquer and the technology for applying it. The novelty is that an approximately 20 cm wide transparent silicone film with a riblet pattern serves as a “stamp”. This is capable of printing patterns with a resolution of a few nanometers, similar to those found in holograms, onto surfaces. The film runs over three flexible rollers and can thus adapt its shape to hug uneven surfaces. From the front, a new type of resin lacquer is continuously sprayed onto the film and transferred with the help of the rollers onto the surface to be treated. A UV lamp then hardens the resin in a fraction of a second. Because of the extremely fast application and hardening process, the riblet structure is retained.

“Our trial lacquer is based on the chemistry used in aviation paints. It is mechanically very durable and,” Stenzel hopes, “should also be resistant to strong UV radiation at high altitude.” A field trial will soon show whether the lacquer fulfills its promise in practice. However, applications for the new coating system are not restricted to the aviation industry, as Stenzel stresses: “With this technology we can apply any other micro and nano structures to lacquered surfaces.”

Source: Fraunhofer-Gesellschaft

Explore further: Faradair team determined to make hybrid BEHA fly

add to favorites email to friend print save as pdf

Related Stories

Skin with high rust protection factor

Jun 04, 2014

In industrialized countries, corrosion guzzles up to 4 percent of economic performance annually. Substances that protect metals effectively from its ravages are often damaging to the environment or have other ...

Jet-propelled wastewater treatment

Dec 20, 2013

Researchers from the Max Planck Institute for Intelligent Systems in Stuttgart have developed a new method for the active degradation of organic pollutants in solution by using swimming microengines. The ...

Optimizing nanoparticles for commercial applications

Apr 29, 2013

Nanoparticles are used in many commercial products catalysts to cosmetics. A review published today in the Science and Technology of Advanced Materials by researchers in Sweden and Spain describes recent ...

Nanotechnology helps scientists keep silver shiny

Oct 26, 2012

There are thousands of silver artifacts in museum collections around the world, and keeping them shiny is a constant challenge. So scientists are using new technology to give conservators a helping hand. A team of researchers ...

Silver saver: Nanotechnology keeps the shine on silver

Apr 12, 2011

(PhysOrg.com) -- Anyone who's ever polished silver knows that keeping the tarnish at bay is never ending work. But, you may not know that polishing also rubs away some of the precious metal, whether it's your ...

Recommended for you

Faradair team determined to make hybrid BEHA fly

23 hours ago

Aiming to transform their concept into a real success, the Faradair team behind a six-seat Bio-Electric-Hybrid-Aircraft (BEHA) have taken this hybrid aircraft project into a crowdfunding campaign on Kickstarter. ...

How polymer banknotes were invented

Nov 26, 2014

The Reserve Bank of Australia (RBA) and CSIRO's 20-year "bank project" resulted in the introduction of the polymer banknote – the first ever of its kind, and the most secure form of currency in the world. ...

Enabling the hearing impaired to locate human speakers

Nov 26, 2014

New wireless microphones systems developed at EPFL should allow the hearing impaired to aurally identify, even with closed eyes, the location of the person speaking. This new technology will be used in classrooms ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.