Mushroom cloud physics

1. Sep 16, 2004

frogger

Ok i am trying to program a simulation of an atomic explosion that would display the resulting mushroom cloud. in order to do this i need to understand, step by step, what forces occur after the actual nuclear reaction that result in producing the actual mushroom cloud and the other actions that affect the surrounding area e.g. smoke rings, force waves etc.

2. Sep 16, 2004

Staff: Mentor

The force waves are easy - its just a shock wave moving at the speed of sound out from the center of the blast. The pressure drops as a square function of the distance (I think).

The mushroom cloud is smoke in/around the fireball. All it is is a bubble of hot air that rises and expands, trailing a column of smoke. The curl-under at the edges is eddy currents trailing the bubble.

edit: to model both, pick an initial size for the explosion fireball (say, 100m in diameter) and use that as the base for the initial intensity of the shock wave. Then have the bubble rising and expanding at some arbitrary rate (play with the numbers until it looks good).

Last edited: Sep 16, 2004
3. Sep 16, 2004

pervect

Staff Emeritus
I'd model the big hot sphere of gas as a baloon. Assume for simplicity that the temperature and pressure is constant throughout the sphere. Then you should be able to figure out how fast the sphere rises (due to buoyant forces), and how fast the sphere expands (due to pressure). You might even be able to take a rough stab at how fast the sphere cools by radiation, though I'm not sure if assuming it's a black body will give the right results, and I think any calculation that doesn't assume it's a black body will be very hard to guess the numbers for.

There's more detailed physics going on, a quick google found

4. Sep 16, 2004

bd1976

Hmm... Your personal computer has no chance of accurately modelling the effects of such an explosion. Your best bet to make it look good would be particle effects to generate the cloud and perhaps model the explosion as an expanding sphere.

However it would really help if you could provide more details of the purpose of this simulation. Does it need to be a realistic physical simulation or a real-time simulation that could be incorporated into a game for example?

Last edited: Sep 16, 2004
5. Sep 16, 2004

sol2

LQG model is advance in relation to the question of thermodynamics recognition, so we have some modelling here that could help? Develope new methods of photon interaction(like the gasmma ray detection in Glast) and devise qubit assimulation.

The very question here has geometrical significance, and one would have to know the phases of this developement to know where each one of these phases is particular to which developement. That's a generalized view.

Heisenberg's collapsing sphere, is a point, that raises the issues for me, to the relevance of the type of geometrical model(implosion then explosion), that we must assume.

Last edited: Sep 16, 2004
6. Sep 16, 2004

Integral

Staff Emeritus
Sol2,
As best I can tell your post is complete nonsense, please find somewhere else to play.

You fail to appreciate the power of a modern desktop computer. There is no reason that your desktop computer could not do a very nice numerical simulation of this phenomena. The hard part is not the number crunching but setting up a viable mathmatical model of the real physics of the expanding ball of hot gas.

7. Sep 16, 2004

do we actually know why the form takes the shape of a muchroom, and not a sphere? Or are we just assuming that there are certain forces forming it in this way.

8. Sep 16, 2004

Integral

Staff Emeritus
What are you trying to say? Of course there are forces acting that cause it. It happens doesn't it?

9. Sep 16, 2004

Gonzolo

It is a sphere. Like russ_waters said, the stem is rising air (and dust), which follows shortly after the initial burst, and "the curl-under at the edges is eddy currents trailing the rising bubble" (sphere).

10. Sep 16, 2004

pervect

Staff Emeritus
The mushroom shape happens only with the Really Large explosions, according to the URL I posted earlier. It happens when the expanding sphere of gas reaches the tropopause - at that point, it has to expand sideways, rather than go up.

11. Sep 16, 2004

pervect

Staff Emeritus
Yes it is.

12. Sep 16, 2004

sol2

Was that a above ground detonation, or ground zero? I guess in space it might be a little different,eh?You should check out the jets in the Bose Nova

Thanks for your time and don't worry, I won't be posting in this thread again.

Last edited: Sep 16, 2004
13. Sep 17, 2004

Staff Emeritus
Sol you mix up orders of magnitude and levels of interaction when you imply that LQG effects would show up in a meshroom cloud. The cloud is more or less just what you would expect in the atmosphere from intense heating at a point source near the ground. The forces acting are gravity and the hydrodynamic forces, gross interactions of atoms, only a little chemistry.

I know that you believe in some "as above, so below" philosophy, but that is just the consequence of getting so much of your information in the form of pictures and applets instead of in mathematics. Similar looking shapes and effects do not mean the same forces are acting.

14. Sep 17, 2004

Staff: Mentor

Sorta OT, but I was looking for pics of mushroom clouds and I found THIS site with photos of the actual fireball miliseconds after detonation. I've never seen these before. Fascinating.

HERE is a site with mushroom cloud photos.

One thing I may need to clarify, pretty much every explosion with a fireball, not just nuclear explosions, creates a mushroom cloud. http://www.usmc.mil/marinelink/image1.nsf/lookup/2004728115250?opendocument is a mushroom cloud from an exploded ammo depot in Iraq with roughly 4 tons of ammo.

Last edited by a moderator: Apr 21, 2017
15. Sep 17, 2004

pervect

Staff Emeritus
Another good physics site I probably should have recommended is the nuclear weaon FAQ

http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html

It's got a little bit about the fireball physics, and more on the damage effects, scaling with yield, etc. It doesn't have a lot about the mushroom cloud itself, alas, the first URL I posted is probably better for that.

16. Sep 22, 2004

frogger

Thank you all for your help I would say more but I’m short of time today. I'll try and get the few answers you asked later. One thing I would like to say is rus_watters posted a link to a picture of a mushroom cloud from an exploded ammo depot in Iraq. It looks, to me, like what’s happening in that picture is very much like when I make smoke ring (from cigarettes not explosions!); Would some of the same physics apply to both smoke rings and mushroom clouds?