Modeling obstructions in the Fluid Domain

When you create a Fluid Mesh type Fluid Domain simulation object and run the analysis or build the input file, the software automatically searches the selected polygon solid body for enclosed or partially enclosed bodies, here called obstructions. These obstructions are not carved out of the solid body selected for the Fluid Mesh using Boolean commands, but instead simply occupy the part of its interior space. When the software detects such obstructions, it uses their polygon faces and edges to limit the propagation of the mesh. The software does not create fluid elements within these obstructions.

The faces of the fluid elements in the Fluid Mesh are therefore coplanar with any planar polygon faces of the obstructions, and align as closely as possible with any curved polygon faces of the obstructions. The geometry of the obstructions can then be used to define the boundary conditions of the fluid model.

Being able to predict which geometry the software will detect as obstructions is essential for creating geometry that will later be used to model surfaces in contact with the fluid mesh generated by a Fluid Domain simulation object.

When the software generates a Fluid Mesh as part of the input file for an analysis:

• The software detects any single (2D or 3D) sheet or solid body that is wholly or partially enclosed by the Fluid Mesh as an obstruction in theFluid Mesh. The graphic below shows several examples.

• The software detects any number of (2D or 3D) sheet or solid bodies that are wholly or partially enclosed by the Fluid Mesh and that do or do not intersect each other as an obstruction in theFluid Mesh. The graphic below shows several examples.

Note:

With any case, when you create the Fluid Domain, you select CAE geometry in Pre/Post, not part geometry.

Ignoring obstructions

You can specify that a solid or sheet body that would otherwise be treated as an obstruction to the fluid mesh be ignored by the Fluid Domain meshing algorithm. With the Inner Regions to Mesh Through group active, select any body that should not be treated as an obstruction to the fluid mesh. The software then meshes through this body rather than around it when generating the Fluid Mesh.

There is one geometric arrangement of an obstruction in a Fluid Mesh that cannot be ignored. This is the case of an obstruction that is only partially enclosed by the Fluid Mesh, as shown in the first example in this article. Partially enclosed obstructions are always meshed around, ever meshed through.

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