Learning Forum

[Aniket Parida]

Hello 

 

While solving a problrm in hydrodynamic diffraction its showing that "ILLEGAL CONNECTIVITY. Element 305 is joined to element 937 and element 1045." but my geometry is absolutely fine.

I have designed it using Solidworks. How to overcome this error, please help me with this.

 

 

[Mike Pettit]

Hello,

Please can you click on the Mesh object in the Outline tree, and share a screenshot of the mesh that has been generated for the structure?

The illegal connectivity error may also be due to a 'T' junction in the geometry. Do you have any internal surfaces in the vessel?

Mike

[Aniket Parida]

Yes I have an internal surface

 

[Aniket Parida]

Actually it is a hollow cylinder having 3mm thickness

 

[Mike Pettit]

Thanks. From your originial image, it appears that the cylinder has a top surface as well. Is this also 3 mm thick? Is the top surface connected to both of the inner and outer cylinder surfaces? There should be a continuous, undivided space inside the vessel, i.e. no internal walls between the surfaces.

I should also mention that for a hollow cylinder of 3 mm thickness, you will need to use quite a small mesh element size. Strictly, the element size should be no larger than the separation between the surfaces (3 mm). However, you can relax this requirement by turning on the Hydrodynamic Diffraction Analysis Settings option 'Ignore Modelling Rule Violations', which would allow you to increase the mesh element size a bit.

Mike

[Aniket Parida]

you have mentoned about T joint here

So if I join 2 cylinders perpendicular to each other will it show any error somewhere?

[Mike Pettit]

Yes, if you join two cylinders perpendicular to each other and you do not remove any overlapping internal faces, then you will get an error.

The error for a 'T' junction in the surfaces will only show as you try to Solve the analysis, when you will see the 'ILLEGAL CONNECTIVITY' error from the solver.

However, you may also see this error message if there is a problem in the mesh, where two mesh nodes are very close together. This may occur when you import an inexact geometry file, like an IGES file.

One other point to note: if the separation between the surfaces is 3 mm, then you should ensure that the Connection Tolerance in the Mesh settings is less than 3 mm, otherwise the mesher will automatically connect the inner and outer surfaces together. This could also cause the 'ILLEGAL CONNECTIVITY' error.

[Aniket Parida]

if i