Electric honeycomb: Pakistani teen in scientific first
bbc.co.uk
bbc.co.uk
http://iovs.arvojournals.org/data/Journals/IOVS/933248/m_z7g...
They aren't in any textbook. My supervisor, a cytoskeleton biologist of many years' experience, had never seen them before. Nobody seemed to know what they were, or why they had decided to form in my cells that day. I tracked down a few mentions of them in the literature, stretching back decades, but this is the only paper i've found that really looks at them with modern tools:
http://pubs.rsc.org/en/Content/ArticleHtml/2009/IB/b818874b
Perhaps the most interesting thing was that nobody seemed very interested in investigating them. They weren't related to anyone's existing research programmes, so they weren't worth it!
See: https://en.wikipedia.org/wiki/Shadowgraph
Penn State did a lot of pioneering work in and with this technique.
To further strengthen the role of surface charges as the key ingredient responsible for the RWI, we shield part of the oil surface from charge accumulation by creating an ion shadow. An ion shadow forms when an object blocks the path of the charged ions towards the surface of the oil. Even thin objects, like paper, are sufficient to produce a sharp shadow that inhibits charge accumulation on the oil surface. In the absence of surface charges the instability is locally inhibited, as evident from figure 11. Even metal objects produce the same effect when placed in the path of the charged ions. Using Schlieren photography (figure 12), we imaged the corona streamer which shows that the streamer and gas flow stay roughly the same size as the needle diameter, while the instability continues to occur at a larger radius.
As you note, Schlieren photography "uses light from a single collimated source shining on, or from behind, a target object. Variations in refractive index caused by density gradients in the fluid distort the collimated light beam. This distortion creates a spatial variation in the intensity of the light, which can be visualised directly with a shadowgraph system."
Basically the point charge is like the sun emitting light (ions) and if you put something in the way of the grounding plate, you get a shadow (local inhibition of the instability pattern).
Check out the pics on the Schlieren photography page, they're cool: https://en.wikipedia.org/wiki/Schlieren_photography
> "The amount of energy that goes in equals the energy that comes out and thus the flow of electricity is efficient. This way equilibrium is restored,"
EDIT: his paper: http://rsos.royalsocietypublishing.org/content/4/10/170503
https://en.wikipedia.org/w/index.php?title=Draft:Electric_ho...