### Tech Briefs

Improved ADINA CFD Sliding Mesh & Glueing Capability

The sliding mesh and glueing capability of ADINA CFD is improved in version 8.5. It can now be applied to couple subdomains where the sliding mesh surfaces have totally different lengths and finite element discretizations. The capability is also available to model conditions between solid elements and fluid elements. These powerful features were already used to solve the 3D example in the News of June 15, 2007.

While the sliding mesh capability is available for different meshes to slide along each other (like in contact analysis of solids), the capability is also useful to simply glue totally different meshes of different domains together (like also used in the analysis of solids, see News of April 30, 2007, News of January 15, 2007, and News of September 15, 2005). This means that different fluid (and solid) domains can be meshed individually with different element sizes and then compatibly glued together.

Here, we illustrate the use of the improved sliding mesh capability by solving the illustrative 2D problem shown in the following figure.

Schematic of Illustrative Problem and Meshes Used.
Note the different FCBI-C element sizes* on the sliding mesh surfaces

As shown in the schematic, the downward flow in the vertical channel splits into two horizontal channels that move up and down.

The mesh plot of FCBI-C elements shows that the flow region is divided into three subdomains, each having its own mesh. The sliding mesh condition is applied at the surfaces between the different domains. In this example, we see that the sliding mesh surfaces are not matched in size (the long vertical channel is much longer than the widths of the horizontal channels). The vertical channel's boundary is modeled by a (no-slip) wall condition that is automatically applied while the sliding mesh surfaces of the horizontal channels move up and down.*

Of particular importance is the fact that, using the FCBI-C elements, local mass and momentum conservation are fulfilled along the sliding surfaces (as well as in the meshes).

Some results are presented in the movie above and the following two figures. The movie shows the variation of pressure and velocity field distribution, and the two figures show detailed pressure and velocity plots near the interface of the vertical channel and the right horizontal outlet.

Detailed Pressure Plot Around Surfaces

Detailed Velocity Plot Around Surfaces

This sliding mesh and glueing capability is obviously very general and powerful, and can be used to solve many problems in engineering practice.

*This capability is only implemented for FCBI-C elements.