Abaqus Multiphysics / Structural-Acoustic Simulation / Structural-Acoustic Simulation Example

Underwater Explosion Simulation

Simulations are increasingly supplanting expensive live-fire explosive testing in the design and analysis of ships and offshore structures. Simulating the effects of underwater explosions on ship and offshore structures presents several challenges: accurate application of loading from distant explosions, strong coupling effects between the water and the ship, the effects of cavitation, and often modeling the explosion itself. In Abaqus, underwater explosion simulation capability is provided by native functionality in Abaqus/Explicit.

• Far-field explosion modeling:
  • Finite elements for acoustic and solid media
  • Incident wave loading with surface and bottom reflections
  • Fast pressure-based cavitation models
  • ALE-based fluid models for coupling to structures with large deformations
  • Surface-based fluid-solid coupling
  • Interior fluid volumes
  • Infinite elements and nonreflecting boundary conditions
  • Analytical underwater explosion bubble modeling
• Near-field explosion modeling

Examples:

• Twin-hulled surface ship: Abaqus coupled structural-acoustics used for shock analysis of surface naval vehicle. The example shows a catamaran (double-hull boat) subjected to a shock due to an underwater explosion. Abaqus allows including free-surface and cavitation effects in the model. The total acoustic pressure animation is shown here along with the deformation of the boat. The cavitation is shown using a light gray color in the water region.
   
  
• Bow section of a submarine: Underwater shock analysis of a submarine using the coupled structural-acoustics capability of Abaqus. The submarine is modeled with structural details including the free-flood compartments and torpedo tubes subjected to a shock due to an underwater explosion. The total acoustic pressure plots in the water filling the compartments along with the deformation of the structure is shown here.
   
  
• Dynamic deformations of a stiffened submarine pressure hull: this model uses the coupled acoustic-shell capability in Abaqus/Explicit. The fluid exterior is modeled using tetrahedral elements (not shown), coupled to the nonconforming quadrilateral shell elements on the hull surface. The displacement response of the hull to an incident pressure wave is shown in the animations.
   
  
• Free-surface cavitation: The fast pressure-based cavitation model and the nonreflecting boundary conditions are demonstrated in these two movies. The difference between the cavitating and non-cavitating solution is evident, as is the effectiveness of the nonreflecting boundary conditions in Abaqus.