Abaqus allows you to create models that include both Eulerian part instances and Lagrangian part instances. During a coupled Eulerian-Lagrangian analysis, the Lagrangian mesh interacts with the materials in the Eulerian part. Coupled Eulerian-Lagrangian analyses typically offer better interpretation of contact conditions than pure Eulerian analyses, particularly for interactions between fluid and solid materials. During postprocessing, a solid Lagrangian body in a coupled Eulerian-Lagrangian analysis appears to maintain its shape better than a similar body in a pure Eulerian analysis.

Figure 28–2 compares a pure Eulerian analysis (top) and a coupled Eulerian-Lagrangian analysis (bottom) of a steel brick passing through a column of water.

In the Eulerian analysis the water tends to adhere to the sides of the brick, and the brick appears deformed in the final configuration. This apparent deformation is a result of the material volume fraction calculations used for Eulerian materials, as discussed in “Material interfaces” in “Eulerian analysis,” Section 14.1.1 of the Abaqus Analysis User's Guide. On the other hand, the Lagrangian brick maintains its shape as it passes through the Eulerian water, and the water flows around the brick.

Coupled Eulerian-Lagrangian analyses also allow you to capitalize on the strengths of both analysis techniques; for example, you can use the loads on a Lagrangian body moving through an Eulerian material to drive a detailed submodel of the Lagrangian body.

To assemble a coupled Eulerian-Lagrangian model in Abaqus/CAE, simply instance both Eulerian and Lagrangian parts in the same assembly. Coupled Eulerian-Lagrangian analyses can be performed only in Dynamic, Explicit steps. You must create a general contact definition to enable contact between Lagrangian and Eulerian parts. The general contact definition allows interactions between Lagrangian surfaces and Eulerian material instances in the model (see “Defining contact in Eulerian-Lagrangian models,” Section 28.3, for more information). Other interactions, loads, boundary conditions, and predefined fields are applied to the Lagrangian and Eulerian parts in the usual manner.

In most cases the Lagrangian part is assembled inside of the Eulerian part instance. While Lagrangian and Eulerian elements and nodes can overlap, three-dimensional Lagrangian elements cannot occupy the same space as an Eulerian material instance. Therefore, Lagrangian parts must be instanced in an area of void within the Eulerian part instance (i.e., a region with no material assignment). To model a three-dimensional Lagrangian part instance that is completely surrounded by Eulerian material, use the volume fraction tool to create an Eulerian material assignment field that includes a void region corresponding to the Lagrangian part instance (see “The volume fraction tool,” Section 28.5, for details).