Avalanches Simulated With 500,000 Ping-Pong Balls 56
An anonymous reader submits "Ping-pong ball avalanche experiments have been carried out for the last three years at the Miyanomori ski jump in Sapporo, Japan, to study three-dimensional granular flows. Up to 550,000 balls were released near the top of the landing slope. The balls then flowed past video cameras positioned close to the flow, which measured individual ball velocities in three dimensions, and air pressure tubes at different heights. The flows developed a complicated three-dimensional structure with a distinct head and tail, lobes and 'eyes.' See for yourself, it's quite interesting!"
Re:One question (Score:3, Informative)
Anyway, clicking around the site, this prime example of what it's all about:
My current research is concerned with the dynamics of avalanches. Avalanches are sometimes treated as a special sort of granular flow. These have been studied for a long time but because they can have solids, fluid and gaseous properties satisfactory theories do not exist except in special situations. An excellent starting point is Taguchi's Powder Page. To understand these flows better a series of experiments was started last year of ping-pong ball avalanches on a ski jump in the outskirts of Sapporo. Up to 300,000 ping-pong balls were released from the top of the landing slope and their subsequent motion analyzed using video cameras. These flows are a much simpler than real avalanches but they do have similarities and any model that cannot explain these flows will certainly fail on real avalanches. I am developing a model to predict these kind of flows.
Re:Hmm... (Score:5, Informative)
The same thing could be said about an avalanche relative to most of our fluid dynamics models. It is still orders of magnitude more complicated. Which isn't to say that our models aren't quite accurate, they are. But at the same time, they're merely a 'good enough' oversimplification of what's really going on.
Fluid dynamics are an extremely difficult thing to model, and even more difficult to compute. They could challenge most of the supercomputers on the top500 list [top500.org].
In fact, the top computer on there, Earth Simulator, (at well over double second place) has one of it's two primary objectives being the calculation of relatively simple fluid dynamics models across the Earth's entire oceans.
So, to put it summarize my point here, the best fluid dynamics models we have are extremely expensive to compute, and they are still not perfect. The best way to better understand, and therefore better model, what is happening, is still to experiment with real physics. This experiment will help us develop faster-but-still-accurate models, or extremely precise models for fluid behavior. Either way, recording the locations of each 'particle' as they flow is actually research and will provide a solid set of data for future research to build on.
Disclaimer: I work in the petroleum industry, and therefore only have experience with extremely high pressure/small scale fluid dynamics. My extrapolations may not hold true to the broader field of fluid dynamics.
Re:Hmm... (Score:3, Informative)
Yeah, but I think the parent was referring to the lack of thermodynamics-type stuff, like snow or ice's reaction due to the heat of friction.
Discovery.ca recently had a short spot on some kids studying freezing blown bubbles, see http://www.exn.ca/video/?Video=exn20040126-snowbu