why muffle shape like after bomb blast?

Answer 1

I assume you're asking why large explosive blasts are muffin-shaped (known as a "mushroom cloud").

Imagine the original explosive front as spherical, but rising above the ground (you remember hot air rises, right?). As it rises, it begins drawing in air underneath at the center. It continues to rise, and the air (and dirt, rocks, debris, etc.) get drawn up through the center and rotates to the outside -- a big donut-shaped vortex makes up the top of the mushroom cloud.

Answer 2

Mushroom clouds are formed by many sorts of large explosions, though they are best known for their appearance after nuclear detonations. Nuclear weapons are usually detonated above the ground (not upon impact) in order to maximize the effect of their spherical expanding fireball. After immediate detonation, the fireball itself begins to rise into the air, acting on the same principle as a hot-air balloon.

(A quite successful way to analyse the motion, once the hot gas has cleared the ground sufficiently, is as a 'spherical cap bubble' - according to Batchelor, this gives quite good agreement between the rate of rise and observed diameter).

While it rises, air is drawn into it and upwards (similar to the updraft of a chimney), producing strong air currents known as "afterwinds", while inside the head of the cloud the hot gases rotate in a toroid shape. When the detonation itself is low enough, these afterwinds will draw in dirt and debris from the ground below to form the stem of the mushroom cloud.

Detonations produced high above the ground do not create mushroom clouds. The heads of the clouds themselves consist of highly-radioactive particles and other fission products, and usually are dispersed by the wind, though weather patterns (especially rain) can produce problematic nuclear fallout. (Glasstone and Dolan 1977)

Detonations below ground level or deep below the water (for instance, nuclear depth charges) also do not produce mushroom clouds, as the explosion causes the vaporization of a huge amount of earth and water in these instances. Detonations underwater but near the surface can produce mushroom clouds, however, as well as large "Wilson cloud chamber effect" (such as that seen in the well-known pictures of the Crossroads Baker test).

Nuclear mushroom clouds are often also accompanied by short-lived vapor clouds or vapor rings. These are created by the blast wave causing a sudden drop in the surrounding air temperatures, causing water vapor in the air to condense around the explosion cloud.

Answer 3

Are you reffering to the craters that can be formed after a blast?

Answer 4

You're gonna have to be a bit more explicit.


Doug