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CFX Wind turbine mesh trouble and solver failure

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Old   April 27, 2012, 07:24
Default CFX Wind turbine mesh trouble and solver failure
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I am trying to run a simulation in CFX to analyse flow through a DAWT and so far I have been running into a few problems.

The method I have been using is to model the geometry in solidworks and exporting as a parasolid text file which i import into the ansys geometry modeller. I then create a cylindrical enclosure around the geometry and subtract from the enclosure using a boolean.

Ideally I would like to have a hex dominant mesh on my geometry but all I can get is a patch independent tetra mesh and when I try to run the solver on this mesh it causes a failure.

If anyone could give me some ideas for getting a better mesh or a reason why the solver is crashing I would very much appreciate it.
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Old   April 27, 2012, 17:54
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You would have to show the output file so we can see what error messages you are getting.

Meshing is an art - it takes lots of practise and training to do it well. So keep trying meshing ideas and see what works for your case.
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Old   April 27, 2012, 20:53
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Hi Glenn,

Thank you for posting a reply.

When I try to run the solver it initialises and then an error box appears saying "The ANSYS CFX solver exited with return code 1. No results file has been
created." The error output is included below. I have checked the rotation axis and they are all right and I have tried to increase the 'tangential vector tolerance' in cfx-pre but it made no difference. So I guess it has to be a meshing problem. Attached is a picture with the two messages I get when meshing. I could not attach a screen shot of my mesh but I have uploaded a couple of pics to tinypic urls below.

Any advice you could give would be much appreciated.

http://tinypic.com/r/2uy10kz/6
http://tinypic.com/r/1jsyso/6


ERROR #002100080 has occurred in subroutine CHECK_NORMV. |
| Message: |
| The specified velocity vector on the boundary patch |
| |
| Diffuser |
| |
| has a significant normal component at one or more faces. One of |
| these face locations is |
| |
| (x,y,z) = ( 2.98817E-01, 3.43716E-01, 5.59020E-01). |
| |
| The angle between the specified velocity and the element surface is|
| 23.132 degrees at this face. This is considered an error because |
| it implies that the mesh is moving. The following are possible |
| reasons for the error message: |
| 1. There is a setup error; for example, an incorrect axis of |
| rotation. |
| 2. There may be a meshing problem; for example, the nodes on a |
| rotating surface might not lie on the surface of revolution. |
| 3. The boundary is curved and the mesh is very coarse. In this |
| case, you may modify the tolerance by increasing the |
| expert parameter 'tangential vector tolerance wall' |
| from its default of 20 degrees.

Ansys.Core.Commands.UserReadableFailureException: The CFX Solver for system Fluid Flow (CFX) did not produce a results file. Detailed information can be found in the output file for the run.
at Ansys.Addins.Infrastructure.Rsm.Data.SolverTask.Re connect(IFullContext context)
at Ansys.Addins.Infrastructure.Rsm.Data.SolverTask.Wa itForFinish(IFullContext context, Boolean allowBreakWait)
at Ansys.Addins.Infrastructure.Rsm.Data.SolverTask.St art(IFullContext context, ICanStartSolverTask startObject, SolverTaskStartTag startTag, SolverTaskSandboxInformation sandboxInformation, SolverTaskSecInformation secInputInformation)
at Ansys.CFX.CFXCore.Data.CFXSolutionSource.RunSolver WithSolverTask(SolutionSettingsEntity solutionSettings, CFXRunStartAssistant runStartAssistant, UpdateOptions updateOptions)
at Ansys.CFX.CFXCore.Data.CFXSolutionSource.RunSolver (IFullContext context, Boolean forceResume, UpdateOptions updateOptions)
at Ansys.CFX.CFXCore.Commands.UpdateSolutionCommand.E xecute(IFullContext context)
at Ansys.Core.Commands.Concurrency.CommandWorkUnit.ex ecuteInContext(CommandContext subContext, IExecutionEngineCallback tracer)
at Ansys.Core.Commands.Concurrency.BaseWorkUnit.doExe cute(IExecutionEngineCallback executionEngine, CommandContext subContext)
at Ansys.Core.Commands.Concurrency.BaseWorkUnit.Execu te(IExecutionEngineCallback executionEngine, Boolean dontCatchExceptions)
--- Ansys.Core.Commands.CommandFailedException: The CFX Solver for system Fluid Flow (CFX) did not produce a results file. Detailed information can be found in the output file for the run.
CommandName: CFX.UpdateSolution(Container="Solution", UpdateOptions=Set(HeldLicenseId=None, DesignPointUpdateSolveManager=None, DesignPointUpdateQueue=None))
at Ansys.Core.Commands.CommandAsyncResult.WaitForSusp endOrComplete(Int32 milliSecondsTimeout, Boolean exitContext)
at Ansys.ProjectSchematic.Data.ComponentTemplateEntit y.Update(IFullContext context, IProgressMonitor progressMonitor, DataContainerReference container, UpdateOptions updateOptions, List`1 downstream, List`1 allRemaining)
at Ansys.ProjectSchematic.Update.UpdateImpl.updateCom ponent(IFullContext context, UpdateTask task)
at Ansys.ProjectSchematic.Update.UpdateImpl.<>c__Disp layClass1a.<updateComponentAndDependencies>b__19()
at Ansys.ProjectSchematic.Update.UpdateImpl.executeWi thSelectedErrorBehaviour(Op op, UpdateTask forTask)
at Ansys.ProjectSchematic.Update.UpdateImpl.updateCom ponentAndDependencies(UpdateTask task, Boolean& didSomething)
at Ansys.ProjectSchematic.Update.UpdateImpl.checkAndU pdateComponent(UpdateTask task, Boolean& didSomething)
at Ansys.ProjectSchematic.Update.UpdateImpl.doOutstan dingTasks(IEnumerable`1 tasks, Boolean& didSomething)
--- System.InvalidOperationException: Update of the Solution component in Fluid Flow (CFX) failed: The CFX Solver for system Fluid Flow (CFX) did not produce a results file. Detailed information can be found in the output file for the run.
at Ansys.ProjectSchematic.Update.UpdateImpl.doOutstan dingTasks(IEnumerable`1 tasks, Boolean& didSomething)
at Ansys.ProjectSchematic.Update.UpdateImpl.<UpdateCo mponents>d__0.MoveNext()
at Ansys.ProjectSchematic.Commands.UpdateComponentCom mand.<Execute>d__0.MoveNext()
at Ansys.Core.Commands.Concurrency.SuspendableCommand WorkUnit.executeInContext(CommandContext subContext, IExecutionEngineCallback tracer)
at Ansys.Core.Commands.Concurrency.BaseWorkUnit.doExe cute(IExecutionEngineCallback executionEngine, CommandContext subContext)
at Ansys.Core.Commands.Concurrency.BaseWorkUnit.Execu te(IExecutionEngineCallback executionEngine, Boolean dontCatchExceptions)
--- Ansys.Core.Commands.CommandFailedException: Update of the Solution component in Fluid Flow (CFX) failed: The CFX Solver for system Fluid Flow (CFX) did not produce a results file. Detailed information can be found in the output file for the run.
CommandName: UpdateComponent(Component="/Schematic/Component:Solution", Force=True)
at Ansys.Core.Commands.CommandAsyncResult.WaitForSusp endOrComplete(Int32 milliSecondsTimeout, Boolean exitContext)
at Ansys.CFX.CFXCore.Commands.UpdateFromSolverManager Gui.Invoke(GuiOperationContext context, GuiOperationArgs args)
--- System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
at System.RuntimeMethodHandle._InvokeMethodFast(Objec t target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at Ansys.UI.GuiOperationContext.Invoke(GuiOperationMe taData operationData, GuiOperationArgs args)
at Ansys.UI.UIManager.InvokeOperationCore(String pseudoname, OperationDelegate callback, Boolean allowOSMessages, Boolean coreTransaction)
Attached Images
File Type: jpg Fine patch independent mesh Messages.jpg (11.7 KB, 36 views)
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Old   April 29, 2012, 06:49
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The error message is obvious. You have specified a boundary with tangential motion, and the motion you specified has a large normal component. The error message tells you the exact location this occurs at.

And you second image shows a rough edge to your mesh. This is usually caused by a meshing error in ICEM. I think the option you need is "thin cuts".
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Old   April 29, 2012, 08:30
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Thanks for your help. This may sound stupid, but I can't find where the define thin cuts option is.

I have searched all the other posts i could find on the topic and they all say the global mesh settings should be available if I select mesh but I still can't find them. I can't even find any info in the help section on "thin cuts", "define thin cuts", "volume meshing options" or any other related search.

Sorry to pester you about this, I am not very experienced.

Thanks again.
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Old   April 29, 2012, 19:08
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What mesher did you use?
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Old   April 29, 2012, 20:27
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I've used the ANSYS ICEM CFD Mesher in the fluid flow (CFX) Project.
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Old   April 29, 2012, 20:31
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You will have to look in the ICEM help menu under thin cuts. This is not part of the ANSYS help but accessed through ICEM.
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Old   April 29, 2012, 21:05
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Thank you!! I just found it as you replied and am trying to run a mesh with it now. It doesn't seem as automatic as the workbench mesher so I may have some problems, but i'll see how it goes and let you know.
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Old   April 29, 2012, 22:55
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Quote:
It doesn't seem as automatic as the workbench mesher
ICEM is the advanced mesher. It requires quite a bit of practise and skill to use, but you can generate excellent meshes of difficult objects with it. But do not expect to produce good results with it straight off.
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