Navigation Links
Amazing skin gives sharks a push
Date:2/9/2012

Streamlined sharks are legendary for their effortless swimming. George Lauder from Harvard University, USA, explains that the fish have long inspired human engineers, but more recently attention has focused on how the fish's remarkable skin boosts swimming. Coated in razor sharp tooth-like scales, called denticles, the skin is thought to behave like the dimples on a golf ball, disturbing the flow of water over the surface to reduce the drag. But something didn't quite sit right with Lauder. 'All of the shark skin studies were done on flat shark skin mimics that were held straight and immovable. But shark skin moves', recalls Lauder. So, when Masters student Johannes Oeffner joined his lab, Lauder suggested that they take a look at the fluid dynamics of shark skin and its analogues to find out how the fish's motion affects fluid flowing over the rough surface. The duo publishes its discovery that shark skin actually generates thrust to give the fish an additional boost in The Journal of Experimental Biology at http://jeb.biologists.org/.

But first the scientists had to get hold of some fresh shark skin, so they went to a market in Boston where they found several large makos. Back in the lab, Oeffner carefully removed sections from a mako's skin and attached them to both sides of a rigid aluminium foil. Then he immersed the foil in a flow tank, reproduced the swimming motion of a fish by wiggling it from side to side and measured the rigid 'swimming' foil's speed by matching it with the flow of water moving in the opposite direction.

Having measured the foil's swimming speeds with intact skin compete with denticles Oeffner carefully sanded off the denticles and set the foil swimming again. However, instead of slowing down as the duo had expected the denticle-free foil speeded up. So the shark skin's denticle surface impeded the rigid swimmer. 'But then we remembered our premise that the sharks aren't rigid', remembers Lauder, so how would the shark skin perform when flexing like a real fish?

Gluing two pieces of shark skin together to produce a flexible foil, Oeffner repeated the swimming experiment, and this time the denticles had a dramatic effect. The intact skin foil swam 12.3% faster than the sanded skin. The shark's rough surface improved the swimming performance spectacularly.

However, when the duo tested the swimming performance of two shark skin mimics a sharp-edged riblet design and the famous Speedo Fastskin FS II fabric they were in for a shock. Although the riblet surface improved the flexible foil's swimming speed by 7.2%, the dented surface of the Speedo fabric had no effect at all. However, Lauder points out that figure-hugging Fastskin swimming costumes probably enhance the swimmer's performance in other ways.

After proving that the denticles on shark skin significantly improve the fish's propulsion, Lauder and Oeffner were keen to find out how they affect fluid flows around the body. Returning the flexible shark skin foil to the swim tunnel, Oeffner and Lauder captured the water's swirling motion with laser light and realised that in addition to reducing drag, the skin was actively generating thrust.

'That's the number one surprise. It's not just the drag-reducing properties, but the denticles alter the structure of flow near the shark skin in a way that enhances thrust', explains Lauder. He is now keen to design physical models to see how altered denticle arrangements affect fluid flows over the skin and to build a computational model to tease apart the beneficial effects of the skin's thrust and drag reduction.


'/>"/>
Contact: Kathryn Knight
kathryn@biologists.com
44-078-763-44333
The Company of Biologists
Source:Eurekalert

Related biology news :

1. The amazing maze of maize evolution
2. Scientists find amazing new pondlife on nature reserve
3. See amazing new sun images from NJITs Big Bear Solar Observatory
4. Frogs amazing leaps due to springy tendons
5. Rare genetic disorder gives clues to autism, epilepsy, mental retardation
6. Dunn Foundation gives Rice $3M for collaborative research grants
7. Soybean grant gives researchers tools to unravel better bean
8. UBC researcher gives first-ever estimate of worldwide fish biomass and impact on climate change
9. Gardening gives older adults benefits like hand strength and self esteem
10. Gardening gives older adults benefits like hand strength and self-esteem
11. Worlds biggest snake gives climate clues
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/13/2017)... FRANCISCO , Feb. 13, 2017  RSA ... centralized platform that is designed to enhance fraud ... latest release in the RSA Fraud & Risk ... enable organizations to leverage additional insights from internal ... tools to better protect their customers from targeted ...
(Date:2/10/2017)... , Feb 10, 2017 Research ... report "Personalized Medicine - Scientific and Commercial Aspects" ... ... medicine. Diagnosis is integrated with therapy for selection of treatment ... early detection and prevention of disease in modern medicine. Biochip/microarray ...
(Date:2/8/2017)... , Feb. 8, 2017 About Voice Recognition ... to match it against a stored voiceprint template. ... pitch, cadence, and tone are compared to distinguish ... hardware installation, as most PCs already have a ... transactions. Voice recognition biometrics are most likely to ...
Breaking Biology News(10 mins):
(Date:2/16/2017)... DIEGO , Feb. 16, 2017  Dermata ... innovative products to treat a variety of dermatological ... million Series 1a financing and entered into a ... (SVB).  Dermata intends to use the capital for ... making major advancements in the treatment of serious ...
(Date:2/16/2017)... ... 2017 , ... AxioMed announced today the success of the ... completed the procedure on Monday, Jan. 30 at Andrews Memorial Hospital in Kingston, ... degenerative disc disease with radiculomyelopathy, as a result of degenerative cervical discs at ...
(Date:2/16/2017)... BOSTON , Feb. 16, 2017 /PRNewswire/ ... for rare genetic deficiencies that result in ... of a $41 million mezzanine round of ... Ipsen, OrbiMed, MPM Capital, New Enterprise Associates, ... an undisclosed public healthcare investment fund. Rhythm ...
(Date:2/16/2017)... ... February 16, 2017 , ... ... further extended its industry leading Biochemistry Services specifically targeting the rapidly growing ... and methods for the biochemical and biosimilar characterization , product-related impurity ...
Breaking Biology Technology: