Error Message—Improper Element Connectivity

Issue

The following error occurs while the simulation is starting:

Error: Improper Element Connectivity

The list of duplicate nodes is also written in the Status file.

Solution

This error is occurs when the elements in the Mesh Enhancement layers collapse and interfere with neighboring tetrahedral elements. This can occur in narrow gaps that are spanned by only one element or in thin geometry (such as sheet metal) that protrudes into a coarsely-volume mesh.  

The parameter that controls the growth of these layers is called the Thickness Factor. 

The Thickness Factor is how far the Enhancement layers can protrude normal to the wall, relative to the thickness of the original tetrahedral. At a setting of 0.5, for example, the wall nodes move away from the wall, half the distance between the wall and the original node near the wall. Reducing the thickness factor reduces the distance the enhancement layers can extend from the wall.  

To resolve this issue:

From the Mesh Enhancement dialog (on the Mesh dialog), reduce the Thickness factor, and start the analysis again. This may resolve the issue or at least reduce the number of duplicate nodes. Reducing the thickness factor further (usually in increments of 0.05) usually eliminates the problem.

If this occurs during the simulation, and not at startup, Automatic Layer Adaption may be to blame. This typically occurs because the mesh was barely acceptable at the beginning of the analysis. As layer thicknesses were adjusted throughout the analysis, the mesh became distorted beyond acceptable limits.

Automatic Layer Adaption modifies the thickness of the enhancement layers during the analysis based on the turbulent Y+ parameter. 

If Adaption is necessary for the analysis, the best solution is to reduce the Thickness Factor and start the analysis from iteration 0.