Abaqus Unified FEA

Complete solutions for realistic simulation.

Coupled Eulerian-Lagrangian

The Coupled Eulerian-Lagrangian (CEL) approach in Abaqus which provides engineers and scientists with the ability to simulate a class of problems where the interaction between structures and fluids is important. This capability does not rely on the coupling of multiple software products, but instead solves the fluid-structure interaction (FSI) simultaneously within Abaqus.


  • Gas-flow inflated automotive airbags
  • Tire hydroplaning
  • Wave loading on offshore structures
  • Cosmetic product dispensing
  • Fuel tank sloshing
  • High-velocity impact and penetration
  • Soil-structure interaction, such as excavation and


Automotive Airbags for Occupant Safety


Airbags provide occupant safety in automotive crashes by deploying at an extremely high rate upon impact. Typical airbags reach a fully inflated state in about 50 milliseconds, ideally prior to contact with the vehicle occupant. Recently, interest has focused on out-of-position occupant scenarios, wherein the occupant contacts the airbag prematurely, before it is fully deployed. In this case, inflator gas flow within the partially deployed bag plays a primary role in the severity of the occupant/airbag interaction. Accurate simulation of the gas/airbag/occupant interactions requires a fluid-structure capability.


Occupant/airbag interactions involving fully deployed airbags are routinely simulated today by representing the effect of inflator gas as a uniformly distributed pressure inside the bag. This uniform pressure assumption is approximate during the early stages of deployment, so for out-of-position occupant scenarios the inflator gas flow inside the airbag can now be modeled using Eulerian technology in Abaqus. The gas/airbag interaction is captured by an extension of Abaqus' easy-to-use general contact feature, which automatically computes the gas/airbag interface, applies constraints to prevent gas leakage, and creates non-uniform pressure on the airbag surface.

Results or Benefit

The Eulerian technology in Abaqus provides enhanced simulation accuracy during the early stages of airbag deployment by eliminating the assumption of uniform pressure distribution within the airbag. This capability is necessary for accurate safety evaluations of out-of-position occupant scenarios in automotive crash safety.

Tire Hydroplaning

Hydroplaning takes place when a tire is lifted off the road by a wedge of water getting trapped under the leading edge of the tire as it travels through a puddle of water. The speed at which a tire hydroplanes is a function of the vehicle velocity, water depth, vehicle load, tire pressure, and most importantly the tread pattern depth and design. When the tire is unable to remove sufficient water from its path, water lifts the tire completely off the road, causing the vehicle to lose control.

It is important to gain insights on the interaction of a tire with a film of water in order to diagnose the onset of hydroplaning and minimize the tire's propensity to hydroplane. A coupled Eulerian-Lagrangian methodology, using a multi-material Finite Element formulation within Abaqus Unified FEA, is used to analyze the interaction of a tire with the water film. The tire is modeled in a Lagrangian framework and the water in an Eulerian framework. The effect of various parameters on the onset of hydroplaning are investigated using the methodology.