Inspired by the mysterious disappearance flight MH370, this research
trys to find out what happened in the final moments of the flight by
studying water entry process. Water entry problem considers the
dynamic motion of an object upon its entry into the water. It is a
classical problem in applied mathematics and fluid dynamics and is
motivated by several applications such as water landing of aircrafts,
ship slamming and return of space capsules. With the help of large
scale computation, three dimensional Navier-Stokes equations can be
solved numerically with the complexity of two fluid phases,
fluid-structure interaction and turbulence modeling. OpenFOAM is used
for this study.
Dynamic Refinement and Mesh Motion
Unstructured body-fitted mesh is first generated for the aircraft. The mesh can deform as the aircraft moves. At the same time, mesh is automatically refined near the air-water interface. The two kinds of mesh modification interoperates well.
Structural response is calculated based on a free-free beam model subject to dynamics external load. This method can predict global break-up failure, while using very little computational resources.
Similar to the miracle on the Hudson river (US Airways Flight 1549), successful ditching of an aircraft can prevent global structural failure and buy enough time for people on board to get saved. Actually, it is the standard emergency water landing.
This nose-dive situation could happen when aircraft lost power while still trying climb. Interestingly, nose-dive with speed comparable to typical landing speed will not incur global structural failure of the fuselage. This could be a reason why there was no debris fields found for MH370.
Pitch Down Diving
Such pitch down entry is dangerous. The nose will either bounce up or get submerged. In both of the cases, large bending moment will develop and result in global break-up of the fuselage.
A rare footage of aircraft rolling entry is captured for the hijacked Ethiopia Flight 961. It can be found on youtube.