A new approach to invisibility cloaking goes beyond transformation optics and those tiresome Harry Potter analogies. It is instead for us at sea to shield floating objects, like oil rigs and ships, from rough waves and is based on the influence of the ocean floor's topography on the various "layers" of ocean water.
Reza Alam, assistant professor of mechanical engineering at the University of California, Berkeley, will describe at the American Physical Society's (APS) Division of Fluid Dynamics (DFD) meeting how the variation of density in ocean water can be used to cloak floating objects against incident surface waves
"The density of water in an ocean or sea typically isn't constant, mainly because of variations in temperature and salinity," explains Alam. "Solar radiation heats the upper layer of the water, and the flow of rivers and the melting of ice lowers the water density near the surface. Over time, these effects add up to form a stable density stratification of two layers – with the lighter fluid layer on top and the more dense fluid layer below it."
Stratified waters, much like regular surface waves, contain "internal waves," which are gravity waves that propagate between the two layers of water. For the same frequency of oscillation, however, internal waves travel at a much shorter wavelength and slower speed than surface waves.
Both wave types "feel" the ocean floor's influence, which generates an energy transfer.
Zeroing in on this energy transfer, Alam used computer simulations to transform a surface wave into internal wave as it approaches an object – meaning that the wave will pass beneath the object rather than crashing into it. And once the internal wave moves beyond the object, it can be transformed back into a surface wave.
This would be achieved by creating "corrugations" or wavy ripples that are tuned to a specific wavelength on the ocean floor in front of the floating object to be cloaked.
"Cloaking in seas by modifying the floor may play a role in protecting near-shore or offshore structures and in creating shelter for fishermen during storms," says Alam. "In reverse, it can cause the disappearance and reappearance of surface waves in areas where sandbars or any other appreciable bottom variations exist."
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Case For Moon: Gateway For Open Ended Exploration, With Planetary Protection Central - On The SpaceShow
- Why We Get Tired When We Stay Up Too Late
- Sweet Irony: The Environmental Impacts Of GMO Sugar Science Denial
- We’re Not In Europe Any More: BfR Statement On EDCs Embraces The Risk-Based Approach
- The Real Cost Of Milk
- Even Light Drinkers Should Watch For Fatty Liver Disease
- When It Comes To Replicating Psychology Studies, Good Luck
- "Oh, okay, glad you aren't worried about little asteroids. Yes I agree, I haven't come across that..."
- "Hello Dario,no copies are made of the same event - the triggering and the data storage are two..."
- "Yes, as the numbers are averages, there is this possibility - actually it happens all the time..."
- "Climate change has been affected by Al-Nino...."
- "And: Comparative efficacy of homeopathic and allopathic systems of medicine in the management of..."
- Silencing cholera's social media
- More than half of EU citizens questioned now think e-cigarettes are harmful
- DIY sampling kits accessed through gay men's social media unearth new HIV cases
- 'Suggestive evidence' for link between air pollution and heightened stillbirth risk
- Prohibition 2016: Assessing the UK's Psychoactive Substances Act