posted on Mar, 13 2006 @ 05:32 PM
In an explosion the expanding gases push compressed air ahead of their expansion creating the blast wave. It’s reflection can cause a mach stem to
form and this video shows mach stem formation from a conventional explosive
My research so far leads me to believe
that mach reflection can only be achieved with high explosives and that the effect would be pronounced
with high yield high explosives. Mach reflection and also a mach stem are signatures of high explosive - they cannot exist without high explosive.
Note the turbulence at ground level in this picture
which shows the mach stem from two blasts. The blast energy from an above ground blast will cause the pressure at ground level to be slightly greater
than that above this level. This is caused by energy absorption at the ground causing the front at this level to move more slowly.
After the blast pressure drops to atmospheric there is a reversal of air flow and this can be most visually observable at ground level as debris at
very low levels is sucked back towards the centre of the explosion, seemingly in the reverse direction to what would be expected. This is caused by
the “inertia” of the material within the blast wave causing a slight over-expansion.
This is a phenomenon which I believe is most obvious by watching the blast patterns following nuclear explosions but is not limited to those and as
the videos above show can be caused by above ground conventional explosions.
So after an explosion we would expect the debris at ground level to travel generally slightly upwards and towards the source of the blast, caused by
the pressures mentioned above.
Now please examine this video and watch the ground level debris right at the end when the camera operator goes behind a vehicle.
Note the direction that the camera operator runs.
Note the direction of the flow of near ground level dust and debris.
Note the direction from where the dust cloud arrives.
Edit to sort link. Thanks
[edit on 13-3-2006 by gordonross]