9 Replies Latest reply on Apr 6, 2016 10:16 AM by Steven Merryweather

    Problem with meshing in a static study

    Steven Merryweather

      I am undertaking a study on an offshore wind turbine  using a jacket structure as a foundation. I have created the model geometry and applied the loads but when I go to mesh, a few extrusions always fail. I have tried adjusting the mesh parameters, re-drawing the structure and adjusting miscellaneous parameters to try to get the model to run, with no success.

      I have attached the file to view.

       

      Any suggestions/tips are greatly appreciated!

        • Re: Problem with meshing in a static study
          James Riddell

          This is almost always a geometry problem.  Verify that there are no gaps, slivers, etc. and minimize any 'singularities' (point or sharp edge contacts).  You can also try mesh control by part on the offending items and mesh the rest normally.  It's sometimes easier to relate the mesh size to the minimum geometry size.

          • Re: Problem with meshing in a static study
            Nandish Datti

            Tips:

            This problem exists because of some geometrical conflicts.

            1. Do not merge solid bodies or extrusions. This is applicable from Boss-Extrude1 through Boss-Extrude12.

            2. Make sure that the bodies are not intersecting each other (Top barrel is intersecting with the vertical pipe)

             

            If you follow above two tips, you should be able to mesh the entire geometry as shown below

            .               mesh.png

              • Re: Problem with meshing in a static study
                James Riddell

                Obviously it was a geometry problem.  However, I do not agree with the merge comment above.  It is possible to merge bodies and get good FEA results (if done properly). 

                  • Re: Problem with meshing in a static study
                    Nandish Datti

                    In this case some part of the geometry is created using weldments and other using a extrude command. Simulation is automatically assigning beam elements to all weldment bodies. However when we merge solids with weldment structures, assigning elements(solids and beams) will be problematic. Recognizing beam profile would lead to errors and we would end up with warning messages.

                     

                    I agree that while analyzing a multi body part or assembly, contacts between the bodies play very important role. In reality if all the components are welded together then setting the component contact to bonded would resemble the actual condition. This assumption will work efficiently when you have only solid elements in the study. But when we deal with a mixed mesh study we have to make sure that the geometry is proper and the contacts are defined properly.

                     

                    If you want to investigate this behavior follow the below steps. Use the same model attached in this case.

                    1. Go to 'Model' tab

                    2. Rollback the FeatureManager Design Tree till Extrude-Thin1. Thus you will have only tower with solid block on top of it.

                    3. Create a static study.

                    4. Create Mesh. Observe the meshed model.

                    5. Go back to Model tab and Edit Boss-Extrude1. Uncheck the Merge result box.

                    6. Go back to previously created study. Treat the top block body as beam and recalculate the beam joints.

                     

                    Let me know your observations.

                  • Re: Problem with meshing in a static study
                    Steven Merryweather

                    Thank you very much for your advice - I have now successfully meshed the model. However, when I come to run, I get an error message saying "the model is unstable. Check you have applied adequate fixtures to stabilise the model". I have applied fixtures to the four piles located at the bottom of the structure which I believe sufficient to stabilise the model yet I still get the error message.