Il solito cherry picking. PEccato che andando oltre, la Purdue dice...

Problem Formulations

Several problem formulations were investigated with the results sketched by the animations below. A basic hypothesis, informally confirmed with engineers knowledgeable in this subject, is that the bulk of the impact damage is due to the body of fuel in the wing and center tanks. Most of the aircraft structure is light-weight low-mass, and relatively low strength, with the exception of the wheel undercarriage. The experiments are

1. A single body of fluid hits a single column. The purpose of this simulation is to understand the response of a reinforced concrete column subjected to high-speed impact of the fuel in the aircraft tanks. In particular, the relationship between the impact velocity of the fluid and the acceleration of the column has been studied, as have different models of concrete columns.

2. The fuel tank hits three rows of columns. The wing enclosure breaks open and the fluid spills. Wings are modeled without ribs, leading to a balloon effect.

3. The fuel fluid, shaped by the wing tank, hits the columns and destroys those in the first two rows. This simulation does not include a wing enclosure and so can be used to better understand the effect of the wing strength on the fuel dispersal.

4. The right-wing fuel tank hits the first three rows of columns. The fuel is modeled as fluid, and the problem is a mixed arbitrary Euler-Lagrange mesh formulation. The fuel tank disintegrates, and the fuel disperses into the structure. This time, the wing has ribs and the break-up is realistic.

5. Full model run, coarse model formulation, run on the IBM Regatta. Model includes all columns in the simulated frame and the complete aircraft. The model size is approximately 300,000 nodes. The run took about 24 hours for 40 frames covering 0.2 sec real time.

6. Full model run, detailed model formulation, run on the IBM Regatta. Model has 1,000,000 nodes. With 50 frames computed in close to 68 hours, the simulation covers 0.25 sec real time. Several observations stand out:
* The simulation demonstrates that the number of columns destroyed in the facade of the building does not have to correspond to the wing span. The tips of the wings, having less mass, are cut by the columns rather than the wing cutting the columns.
* The simulation suggests that the reinforced concrete column core will cut into the fuselage until the fuel depot reaches it, at which time the column is destroyed.
* The simulation shows the deceleration of the plane after impact as witnessed by the buckling of the fuselage near the tail structure.