14-05-2011, 12:37 PM
Yes material is being forced laterally out of the window openings and the aluminum skin is popping off. The towers contained millions of cubic feet of air which had to be disbursed by the collapsing debris. This air was forced away from the collapsing debris of course... and there was a negative pressure behind the collapse front which pulled air from above in and behind the collapse. If you drop a mass in relatively still air you can observe the same flow of air caused by the dropping mass.
The air on each floor was forced away from the collapse front and it shattered the glass and carried with it small debris - lightweight crushed ceiling panels, pulverized wall board and small building contents. This expulsion took place just ahead of the crush front. What you are seeing is not explosions but half million cubic feet of pressurized air forced away (displaced) by the driving massive destructive debris/rubble and floor matter at each floor. That's a lot of air to displace in one tenth of a second. And if you don't think air can be destructive... stand around in 3-400 mph winds with sand and other material carried in the air. Consider that the air inside a single floor was moved out of the way in .1 seconds which is the rate that the collapse was measured at. The air located mid span of the floor would be 30 feet from the facade and would have to move that 30 feet in the 1/10 of a second that the collapse front pushed through the floor. If that section of air mid 60 foot span of the floor reached the window in 1/10 of a second... which it did.. it would have had to have traveled at over 400 mph.
Air moving at 400 miles an hour exerts over 600 pounds per square inch of pressure (600psi). And that's enough to shatter the glass and carry and expel the contents. Anyone who has seen a tornado or a hurricane should know how powerful wind is at such speeds. Winds of 100 mph exert 27.5 psi. Basic physics explains the expulsions seen coming from the collapse front. Here is the destructive force of explosive overpressure from http://www.workingfire.net/misc12.htm:
Calculate the pressure of an explosion:
The air on each floor was forced away from the collapse front and it shattered the glass and carried with it small debris - lightweight crushed ceiling panels, pulverized wall board and small building contents. This expulsion took place just ahead of the crush front. What you are seeing is not explosions but half million cubic feet of pressurized air forced away (displaced) by the driving massive destructive debris/rubble and floor matter at each floor. That's a lot of air to displace in one tenth of a second. And if you don't think air can be destructive... stand around in 3-400 mph winds with sand and other material carried in the air. Consider that the air inside a single floor was moved out of the way in .1 seconds which is the rate that the collapse was measured at. The air located mid span of the floor would be 30 feet from the facade and would have to move that 30 feet in the 1/10 of a second that the collapse front pushed through the floor. If that section of air mid 60 foot span of the floor reached the window in 1/10 of a second... which it did.. it would have had to have traveled at over 400 mph.
Air moving at 400 miles an hour exerts over 600 pounds per square inch of pressure (600psi). And that's enough to shatter the glass and carry and expel the contents. Anyone who has seen a tornado or a hurricane should know how powerful wind is at such speeds. Winds of 100 mph exert 27.5 psi. Basic physics explains the expulsions seen coming from the collapse front. Here is the destructive force of explosive overpressure from http://www.workingfire.net/misc12.htm:
GLASS SHATTERING : 0-5 PSI
FIREFIGHTER KNOCKDOWN: 1.PSI
WOOD PARTITION COLLAPSE : 1-2 PSI
CINDER BLOCK WALL COLLAPSE: 2-3 PSI
BRICK WALL COLLAPSE : 7-8 PSI
FIREFIGHTER LUNG DAMAGE : 15 PSI
THRESHOLD FOR FATALITIES: 35 PSI
50% FATALITIES: 50 PSI
99% FATALITIES: 99 PSI
One can see how destructive over pressure is and how this easily explains the observations.FIREFIGHTER KNOCKDOWN: 1.PSI
WOOD PARTITION COLLAPSE : 1-2 PSI
CINDER BLOCK WALL COLLAPSE: 2-3 PSI
BRICK WALL COLLAPSE : 7-8 PSI
FIREFIGHTER LUNG DAMAGE : 15 PSI
THRESHOLD FOR FATALITIES: 35 PSI
50% FATALITIES: 50 PSI
99% FATALITIES: 99 PSI
Calculate the pressure of an explosion:
That initial pressure will decrement as the volume expands adiabatically from V0 to V; where V = 1/2 4/3 pi r^3 (The 1/2 accounts for a hemisphere.) So, the pressure upon expanding becomes P = nRT0/V; where T0 remains the same as this is an adiabatic expansion. (In a non-ideal case, aka reality, this would not be the case, but the P derived would serve as an upper bound with the expectation the real P would be somewhat less.)
Therefore P/P0 = nRT0/V//nRT0/V0 = V0/V and P = P0 (V0/V) = P0 (V0/[2/3 pi r^3]); where r = 10 meters. If you measure P0 at ground zero, say, r0 = 1 meter, you can write P = P0 (r0/r)^3 = P0 (1/r^3) when r0 = 1 meter where P0 was measured.
Bottom line, ideally, pressure decrements inversely with the cube of the distance from ground zero.
Explosive advocates can calculate the explosive force and location of the explosives based on the measured cloud and ejection speed. Be my guest.
Therefore P/P0 = nRT0/V//nRT0/V0 = V0/V and P = P0 (V0/V) = P0 (V0/[2/3 pi r^3]); where r = 10 meters. If you measure P0 at ground zero, say, r0 = 1 meter, you can write P = P0 (r0/r)^3 = P0 (1/r^3) when r0 = 1 meter where P0 was measured.
Bottom line, ideally, pressure decrements inversely with the cube of the distance from ground zero.