LibriumArcana.Games

sciencedaily.com wrote:A new approach to invisibility cloaking may one day be used at sea to shield floating objects -- such as oil rigs and ships -- from rough waves. Unlike most other cloaking techniques that rely on transformation optics, this one is based on the influence of the ocean floor's topography on the various "layers" of ocean water.

At the American Physical Society's (APS) Division of Fluid Dynamics (DFD) meeting, being held November 18-20, 2012, in San Diego, Calif., Reza Alam, assistant professor of mechanical engineering at the University of California, Berkeley, will describe 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."

rhoenix wrote:This is just mind-boggling. Real-world science nowadays is so much cooler than anything scifi can come up with.

Josh wrote:An article I was reading on my phone last week took it a step further and hypothesized seismic cloaks for friggin' cities. That might be some pie in the sky-ass 50s flying car bullshit, but it's a nice dream.

rhoenix wrote:I dunno, man. Stuff like that will get dusted off the shelf when it comes time to plan cities on another planet. It probably won't happen here, at least barring a huge disaster of some kind of motivate people, since society's momentum does have an impact on adoption of new shiny stuff.

On the other hand, other stuff from tech is creeping in all the time, like traffic cameras, tagging, and smartphones. In a hundred years, it may not be fiction at all, but part of good city planning.

rhoenix wrote:I hear you - it's just that we humans have this whole "what I think of as normal is best! Get away from me with your newfangled gizmos!" thing.

Then again, that could be just overt cynicism - you're very right in that Japan would be very interested in such a thing, and if current global climate change trends continue, it won't just be them.