Flow visualisation of a cavitating hydrofoil as part of a preliminary test validation study for a large numerical and physical research project.

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UNDEX Evaluation


Underwater explosions (UNDEX) present complex dynamic material behaviours that can be difficult to model accurately. The ESI Group's Virtual Performance Solutions (VPS) software suite has integrated fluid and structural solvers that handle this task efficiently.

The explosion is modelled as a controlled release of energy in Smoothed Particle Hydrodynamics, SPH. The development and propagation of the pressure pulse in the fluid is also modelled in SPH. The fluid interacts with the ship through robust contact interfaces, and the fully structural model of the ship is modelled as conventional finite elements with failure. The complete simulation process occurs within the one suite of software.

If the hull is breached, a second simulation is then able to model the flooding of the hull. This is conducted using SPH and allows the vessel to respond to the incoming water by trim, roll and sinkage until a new equilibrium is achieved.

Images below show, (clockwise from top left) the UNDEX event, the resulting damage, flooded vessel with list to port, close up of the breach of the hull caused by the UNDEX event.

UNDEX damage assessment images from a VPS solution model.

Searchable Keywords

  1. UNDEX, Underwater Explosion
  2. Blast analysis
  3. Ship damage
  4. Ship stability