5 ms·

The air canon itself is very interesting, and I don't fail to appreciate it. I'd very much enjoy seeing a video or reading in-depth about how one is designed a

by shpxnvz 16y ago

The air canon itself is very interesting, and I don't fail to appreciate it. I'd very much enjoy seeing a video or reading in-depth about how one is designed and constructed, or about real-world uses for such a technology. I do fail to appreciate a video that is entirely focussed on using one to knock things down, when said things are obviously constructed to be as weak and fragile as possible. Thus, the reaction of the presenter seems to me somewhat contrived and incongruous. It appears on the face to be typical over-the-top T.V. production and I, personally, don't find it particularly impressive. Since you are obviously involved in this stuff, do you have any links to some material that talks about the technology itself? That I would appreciate.

RiderOfGiraffes 16y ago
Let me start by apologising. My comments were snarky and I shouldn't've said what I did. It's now too late to edit them, but perhaps it's better to let them stand anyway. With regards links, no, I don't have any links to pages explaining the technology. The best I have is this one: http://www.eskimo.com/~billb/amateur/vortgen.html http://www.eskimo.com/~billb/amateur/vortgen.html There's a lot of stuff scattered around, but I've never found a single, coherent treatment. The reason smoke/air/fluid rings happen, in short, is this. Throw a lump of air forward. The air in front of it gets pushed outwards to let the lump through. As the displaced air streams around the outside, it drags on the lump, causing the front face of the lump to follow the displaced air. That makes the front flow around the outside, and then the back comes forward through the middle to replace the air at the front, and hence you get a toroidal circulation. (in truth it's more complex, but that's the basic idea) Here's an animation that shows the idea. http://www.amasci.com/wing/smring.html http://www.amasci.com/wing/smring.html That site has much that's poorly expressed, so don't take it all too seriously. Making air/fluid rings is pretty easy, just throw a lump at a sensible speed. They turn up everywhere, but there are some surprises. Send a smaller, faster ring after a larger, slower one. The faster one catches up and goes through the larger one. The larger one even gets bigger to let it through, then shinks, catches up and goes through the other. You can get "leap-frogging" smoke rings, which is cool. http://serve.me.nus.edu.sg/limtt/video/leapfrog.mpeg http://serve.me.nus.edu.sg/limtt/video/leapfrog.mpeg All the basic fluid-dynamic ideas are Newtonian in principle and you can treat air as incompressible, near frictionless marbles flowing around. Until you can't. ADDED IN EDIT: Collisions between smoke rings are interesting, both head-on and oblique. Most of the time you get a spray of smaller rings, each made half from one, half from the other. Or so I'm told - I'm still hoping to get the opportunity to explore that situation sometime. HA! Found video: http://serve.me.nus.edu.sg/limtt/video/collision.mpeg http://serve.me.nus.edu.sg/limtt/video/collision.mpeg http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_front.mpg http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_fron... http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_top.mpg http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_top.... http://serve.me.nus.edu.sg/limtt/#Video_Gallery http://serve.me.nus.edu.sg/limtt/#Video_Gallery Finally, bit puzzled as to why this comment is getting down-modded at the moment since I'm trying to contribute interesting stuff. My guess it's the same person who down-modded the grandparent to this comment, and wants to punish it further. <shrug> I'll live with that - it was more snarky than I intended, and inappropriate for HN. We all make mistakes.
- frossie 16y ago
  Since I made the original objectionable comment I would just like to say that shpxnvz explained my annoyance very well. The issue is not the technology, it is the way they chose to demonstrate it by riffing off the three little pigs but then cheating the demo to fit their narrative. I personally detest this kind of "whizz bang gloss over the details" style of science show. I am one of those sad and pathetic individuals who think science and technology are intrinisically exciting without needing to resort to cheap tricks. I also hate being told how to feel - the dude is the science show equivalent of a laugh track and really grated on me. There is an argument that one has to resort to this kind of presentation in order to engage kids. I find this patronizing and it does not match my own limited experience talking at schools, but I concede I could be wrong.
  - timthorn 16y ago
    If I remember the (full) episode correctly, the presenter went into a good level of detail about the working of the cannon, showing a prototype in the lab and explaining what was happening. What is on YouTube is just the conclusion of the experiment. This is clearly a marketing clip; Bang Goes the Theory is a pretty good attempt at a science show, and indeed is an Open University show.
- shpxnvz 16y ago
  Thanks for the apology, and the links that you did have. Those were much more interesting videos, I thought. And it would particularly cool to see a vortex blimp in action. Oh, for the record, you got an up-vote from me.

by shpxnvz 16y ago

RiderOfGiraffes 16y ago

Let me start by apologising. My comments were snarky and I shouldn't've said what I did. It's now too late to edit them, but perhaps it's better to let them stand anyway. With regards links, no, I don't have any links to pages explaining the technology. The best I have is this one: http://www.eskimo.com/~billb/amateur/vortgen.html http://www.eskimo.com/~billb/amateur/vortgen.html There's a lot of stuff scattered around, but I've never found a single, coherent treatment. The reason smoke/air/fluid rings happen, in short, is this. Throw a lump of air forward. The air in front of it gets pushed outwards to let the lump through. As the displaced air streams around the outside, it drags on the lump, causing the front face of the lump to follow the displaced air. That makes the front flow around the outside, and then the back comes forward through the middle to replace the air at the front, and hence you get a toroidal circulation. (in truth it's more complex, but that's the basic idea) Here's an animation that shows the idea. http://www.amasci.com/wing/smring.html http://www.amasci.com/wing/smring.html That site has much that's poorly expressed, so don't take it all too seriously. Making air/fluid rings is pretty easy, just throw a lump at a sensible speed. They turn up everywhere, but there are some surprises. Send a smaller, faster ring after a larger, slower one. The faster one catches up and goes through the larger one. The larger one even gets bigger to let it through, then shinks, catches up and goes through the other. You can get "leap-frogging" smoke rings, which is cool. http://serve.me.nus.edu.sg/limtt/video/leapfrog.mpeg http://serve.me.nus.edu.sg/limtt/video/leapfrog.mpeg All the basic fluid-dynamic ideas are Newtonian in principle and you can treat air as incompressible, near frictionless marbles flowing around. Until you can't. ADDED IN EDIT: Collisions between smoke rings are interesting, both head-on and oblique. Most of the time you get a spray of smaller rings, each made half from one, half from the other. Or so I'm told - I'm still hoping to get the opportunity to explore that situation sometime. HA! Found video: http://serve.me.nus.edu.sg/limtt/video/collision.mpeg http://serve.me.nus.edu.sg/limtt/video/collision.mpeg http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_front.mpg http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_fron... http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_top.mpg http://serve.me.nus.edu.sg/limtt/video/Oblique_collison_top.... http://serve.me.nus.edu.sg/limtt/#Video_Gallery http://serve.me.nus.edu.sg/limtt/#Video_Gallery Finally, bit puzzled as to why this comment is getting down-modded at the moment since I'm trying to contribute interesting stuff. My guess it's the same person who down-modded the grandparent to this comment, and wants to punish it further. <shrug> I'll live with that - it was more snarky than I intended, and inappropriate for HN. We all make mistakes.

frossie 16y ago
Since I made the original objectionable comment I would just like to say that shpxnvz explained my annoyance very well. The issue is not the technology, it is the way they chose to demonstrate it by riffing off the three little pigs but then cheating the demo to fit their narrative. I personally detest this kind of "whizz bang gloss over the details" style of science show. I am one of those sad and pathetic individuals who think science and technology are intrinisically exciting without needing to resort to cheap tricks. I also hate being told how to feel - the dude is the science show equivalent of a laugh track and really grated on me. There is an argument that one has to resort to this kind of presentation in order to engage kids. I find this patronizing and it does not match my own limited experience talking at schools, but I concede I could be wrong.
- timthorn 16y ago
  If I remember the (full) episode correctly, the presenter went into a good level of detail about the working of the cannon, showing a prototype in the lab and explaining what was happening. What is on YouTube is just the conclusion of the experiment. This is clearly a marketing clip; Bang Goes the Theory is a pretty good attempt at a science show, and indeed is an Open University show.
shpxnvz 16y ago
Thanks for the apology, and the links that you did have. Those were much more interesting videos, I thought. And it would particularly cool to see a vortex blimp in action. Oh, for the record, you got an up-vote from me.