Discussion Forum

Degenerate (not "degenerated") elements are generally tied to problems with the geometry. From the Comsol Multiphysics help system:

A degeneracy in the geometry can occur during solid modeling. For example, fillet areas that taper to a point and the apex of a cone can become degenerate points. These degeneracies might cause problems for the mesh generator and during the analysis. A common degeneracy in the geometry occurs when a 3D solid is created (for example, a cylinder) by rotation about an axis that touches the rotation area. It is then better to create the solid object by extruding a cross section or to use geometric 3D primitives.

Also, from the help system:

AVOIDING EXCESSIVELY SMALL DETAILS, HOLES, AND GAPS. Many geometries, especially those designed using a CAD system, contain small holes, details, and gaps. These small features can make the domain unbounded and must be removed before analysis. Small details and holes can lead to large meshes or even failure during mesh generation. Make sure the snapping feature is activated to avoid small gaps and mismatches between the geometry objects. The CAD Import Module contains tools for automatic and interactive repair and defeaturing of 3D CAD data. For a 2D or 3D model you can also remove small details and prepare the geometry for efficient meshing using virtual geometry operations (see Virtual Geometry Operations).

So I suggest you work on modifying or fixing-up your geometry using whatever tools are available to you in both the exporting and importing processes, or a combination of them.

In regard to mesh quality, yes, you can make plots showing the mesh quality and identifying if, and where, mesh quality is poor. In the Model Builder, right-click on Mesh, then click on Plot. The default is a plot of mesh quality.

I tried to import a part of model and it ran through. However, I found that it was imported as geometry, which was not I wanted. Can I directly imported the mesh?

I think so. In the Model Builder, right-click on Mesh, then click on Import.

Ok, I nailed down the problem. Some elements have duplicated nodes and it is not allowed in COMSOL. I have to turn them all into tetrahetric elements.