Scientifically Based 911 Animation
Simulation shows effects of
plane crash on WTC
LAFAYETTE, Ind., June 13 /Standard Newswire/ -- Although most
Americans believe they know what brought down the World Trade Center
twin towers on Sept. 11, 2001, civil engineers are still seeking
answers to questions that could save lives in the future.
engineers need to know from a scientific perspective what happened
to the buildings during the terrorist attacks in order to prevent
future failures. The search for answers continues with the help of a
state-of-the-art animated visualization created by researchers at
Hoffmann, a professor of computer science and director of Purdue's
Rosen Center for Advanced Computing, a division of Information
Technology at Purdue, says the animation reveals more information
than could be conveyed through a scientific simulation alone.
simulations restrict us to showing the things that are absolutely
essential to the engineer," Hoffmann says. "This gives us a
simulation that doesn't deliver much visual information to a
layperson. Our animation takes that scientific model and adds back
the visual information required to make it a more effective
simulation, the completion of which was announced last September,
required several test runs before the researchers were satisfied;
the final test run required more than 80 hours of high- performance
computing. The simulation depicts how a plane tore through several
stories of the World Trade Center north tower within a half-second
and found that the weight of the fuel acted like a flash flood of
flaming liquid, knocking out essential structural columns within the
building and removing fireproofing insulation from other support
structures. The simulation used lines and dots to show the aircraft
and building during the event.
To develop the
new animated visualization, Voicu Popescu, an assistant professor of
computer science, developed a translator application that creates a
link between computer simulations and computer visualization systems
to automatically translate simulation data into a 3-D animation
translator is scalable and can be used in other simulations,"
animation, elements that were not part of the scientific simulation,
such as flames and smoke, are clearly rendered, although the
visualization does not show the subsequent effects of the fire.
details were added in this animation, Popescu says the visualization
was intentionally kept "non-descript" so that they would not be
exploitive of the horrific attack.
on the airplane there are no airline insignia or windows," Popescu
says the visualization has a realism never seen before.
and computer models you often see on television are not
scientifically accurate," he says. "This provides an alternative
that is useful to the nonexpert but is also scientifically accurate,
so it provides a more realistic picture of the event."
visualization begins with a Google Earth map of lower Manhattan as
it appeared on Sept. 11, 2001. The video then shows the damage
caused by the aircraft as it hit the north tower, follows the
disintegrating plane through the interior, and then shows the
airplane metal, ignited fuel, dust and smoke exiting the building on
the opposite side.
found that the airplane's metal skin peeled away shortly after
impact and shows how the titanium jet engine shafts flew through the
building like bullets.
As with an
earlier simulation developed by this team that examined the 9/11
attack on the Pentagon, the World Trade Center simulation showed
that it was the weight of the 10,000 gallons of fuel more than
anything else that caused the damage.
"It is the
weight, the kinetic energy of the fuel that causes much of the
damage in these events," Hoffmann says. "If it weren't for the
subsequent fire, the structural damage might be almost the same if
the planes had been filled with water instead of fuel."
Purdue's Kettlehut Distinguished Professor of Structural Engineering
and a principal investigator on the simulation project, says the
researchers worked for years and used the best computing resources
available to recreate the event.
the serious damage to the World Trade Center core columns, we
assembled a detailed numerical model of the impacting aircraft as
well as a detailed numerical model of the top 20 stories of the
building," Sozen says. "We then used weeks of supercomputer time
over a number of years to simulate the event in many credible angles
of impact of the aircraft."
Sozen says the
actual damage to the building's facade that was observed was
identical to the damage shown by the numerical simulation.
our calculations using data from experiments we had conducted to
evaluate the energy imparted from fluid moving at high speed to
solid targets," he says. "We concluded that the damage map we
calculated for our numerical model of the building would correspond
closely to the actual extent of the damage."
represented the plane and its mass as a mesh of hundreds of
thousands of "finite elements," or small squares containing specific
physical characteristics. In the visualization, these scientific
data points are used to show how airplane components swept through
the building and out through the other side as the fuel ignited.
moved through the building as if it were a hot and fast lava flow,"
Sozen says. "Consequently, much of the fireproofing insulation was
ripped off the structure. Even if all of the columns and girders had
survived the impact - an unlikely event - the structure would fail
as the result of a buckling of the columns. The heat from an
ordinary office fire would suffice to soften and weaken the
unprotected steel. Evaluation of the effects of the fire on the core
column structure, with the insulation removed by the impact, showed
that collapse would follow whatever the number of columns cut at the
time of the impact."
is the latest in a series of projects by the Purdue team that arose
after 9/11 to determine the structural damage that occurs when an
airplane collides with a building. Although one goal was to develop
structures that can withstand a terrorist attack, the team also has
used this research to investigate other scenarios, such as an
airplane inadvertently crashing into a building located near an
important work that has many more applications than we first
thought," Hoffmann says. "The important thing is that we are
learning so much in so many different areas."
was funded in part by the National Science Foundation.
involved in the research are civil engineering assistant professors
Ayhan Irfanoglu and Santiago Puiol, computer science doctoral
student Paul Rosen, and civil engineering doctoral students Oscar
Ardila and Ingo Brachmann.