Learning Forum

[ridoykarmoker1815]

Hello,
Currently I'm doing my BSc thesis and I needed to do a model of circular cylinder for Ansys Aqwa. While running the analysis in hydrodynamic diffraction this error message is showing. If anyone can help me, it would be very beneficial.

[Mike Pettit]

Hello,

Please open the solver files directory for this analysis in Windows Explorer - if your project is saved as 'MyProject.wbpj', the solve files directory will be located in MyProject_files\dp0\AQW\AQW\AQ\Analysis. Open the Aqwa input file, ANALYSIS.DAT, using a text editor (e.g. Notepad). Scroll down through the file to see if there is anything unusual, for example an error message (just searching for 'error' might help). From the Aqwa output in your image, it looks like there is a problem in the element data. Please screenshot anything you find (don't attach the DAT file itself - as an Ansys employee I'm not allowed to download it from this thread).

We have encountered problems with imported geometries (i.e. not created directly in DesignModeler or SpaceClaim) which include Line Bodies, where the vertices of adjoining lines are not exactly coincident. Please check the geometry carefully to see if there are any very short line segments.

Cheers, Mike

[ridoykarmoker1815]

Hi, sorry for late.There is an error message how you directed. Can you guide me how to solve this message?

[ridoykarmoker1815]

The meshing deatils shows this message.

[ridoykarmoker1815]

Dear Mike Pettit, thanks for your reply. I run the problem in ansys aqwa and somehow reach to a solve. This time no error message in ANALYSIS.DAT file. But there is warning messages saying the elemens aren't connected. Is there any way to check the co-ordinate value of those elements? Because It's necesaary to know the location of the elements which are creating those warning messages.Getting reply from you would be very benficial.

[Mike Pettit]

Hello,

What was the original geometry source you used to define the model? I guess it may have been an imported external file (e.g. IGES file), rather than created from scratch in SpaceClaim. You may find that the SpaceClaim Repair tools are useful here:

For your model, you might try:

• Stitch: combines disconnected surfaces into a single surface body
• Gaps: fills small gaps between faces, which may be causing the 'UNDERWATER SIDE...' warnings that you are seeing; you may need to increase the maximum distance setting in Options - Find/Fix:

• Small Faces: merges small or thin faces into adjacent faces, which may improve the mesh quality; you may need to increase the maximum area and width settings:

Cheers, Mike

[ridoykarmoker1815]

Dear Mike,

Thank You for your valueable comments on my problem. I have now started to model in ansys design modeler rather than to import files, which helped me a lot. I'm now stuck in a problem on designing Morison Elements(identical to spider web in bottom).Can you please help me on how I can model Morison Element in ansys and join that with the main cylinder body?

[Mike Pettit]

Hello,

It looks like you have already got everything defined as it should be. In the DesignModeler Outline tree, make sure that the Line Bodies and Surface Bodies are all collected into a single Part. When you import this geometry into Aqwa Workbench, the Line Bodies will be automatically written as Morison elements in the Aqwa input file.

Cheers, Mike

[ridoykarmoker1815]

Dear Mike,

I've kept the line body and surface body in a single part. But, the results came same as a cylinder without morrison element. I'm sure that the result must change with the insert of morrison element. Can you give any idea about this?

 

[Mike Pettit]

Hello,

In the Hydrodynamic Diffraction analysis, under Analysis Settings, you should turn on the Linearized Morison Drag option. Then, right-click on Hydrodynamic Diffraction and Insert > Irregular Wave to define a wave spectrum. This spectrum is used for the drag linearization calculation. When you re-run the diffraction analysis, you should find that the RAOs have changed due to the damping effect of the Morison drag.

Cheers, Mike