[visitor]

Can anyone help out on this please?

Its an internal combustion piston simulation.

The fuel inlet, air and exhaust inlets flows are controlled by atstep limits, if conditional statements.

The piston moving wall follows a cosine wave velocity, see attached image.

Thanks


Details of error:-
----------------
Error detected by routine PSHDIR
CDRNAM = SOLUTION/ZN1 /BELG8 /BIP/LIN_COEFS/PRES /VEL_FL1
CRESLT = NONE

Current Directory : /FLOW/ASSEMBLE/TIME-0

+--------------------------------------------------------------------+
| Writing crash recovery file |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Stopped in routine MEMERR |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| The ANSYS CFX solver exited with return code 1. No results file |
| has been created. |
+--------------------------------------------------------------------+

End of solution stage.

+--------------------------------------------------------------------+
| The following transient and backup files written by the ANSYS CFX |
| solver have been saved in the directory F:/ice/my |
| ice_pending/dp0_CFX_Solution/Fluid Flow CFX_002: |
| |
| 0_full.trn |
+--------------------------------------------------------------------+


+--------------------------------------------------------------------+
| Warning! |
| |
| The ANSYS CFX Solver has written a crash recovery file. This file |
| has been saved as F:/ice/my ice_pending/dp0_CFX_Solution/Fluid |
| Flow CFX_002.res.err and may be an aid to diagnosing the problem |
| or restarting the run. More details should be available in the |
| solver output section of the output file. |
+--------------------------------------------------------------------+


+--------------------------------------------------------------------+
| The following user files have been saved in the directory |
| F:/ice/my ice_pending/dp0_CFX_Solution/Fluid Flow CFX_002: |
| |
| trace, mon |
+--------------------------------------------------------------------+


+--------------------------------------------------------------------+
| For CFX runs launched from Workbench, the final locations of |
| directories and files generated may differ from those shown. |
+--------------------------------------------------------------------+


This run of the ANSYS CFX Solver has finished.

[ghorrocks]

You cannot diagnose it with the information you provided.

I would do a model with just the piston motion (is it the moving mesh?), the valves (is it the boundary condition?) and both together (is it a combination of moving mesh and the boundaries?). But if I was a betting man I would put money on the problem being your valve boundary conditions. They look like numerical nightmares to me.

Also: A crankshaft/conrod/piston assembly does not result in a sinusoidal motion. It is close but has significant differences. If you want to be accurate you will need to put the correct motion in.

[visitor]

Thanks for your reply G.

Inlets and outlets are just boundary conditions, the inlet valve is a pressure inlet at 1.1 bar, the outlet valve is an opening boundary condition.

Piston motion for now is just a sign wave, but will be refined once the problem is resolved.

I don't know about moving mesh, I think dynamic mesh selection as shown in attached screen shot is sufficient 'Basic Settings'

[ghorrocks]

Have you done a run with just moving mesh as I suggested? That, remove the valve and just compress the gas. This is a very useful validation as if you make the walls adiabatic then the gas temperature and pressure should follow the adiabatic compression curve. This will help you determine the convergence and time step size required for accuracy.

Then do a model with the valves but no mesh motion. Maybe replace the piston with an opening and pull some flow through. I bet this does not work in your case as the way you have set the valve up is unlikely to work in my opinion (but this test will show it).

Finally: Do not post screen dump images of your model. If you want us to understand what you are doing please attach images of your mesh and your output file.

[visitor]

Please find attached sectional mesh view.

I don't think an opening BC with flow pulled in can represent piston movement, so I will be continuing attempts to make it work in it's simplicity. CCL file can be sent to you if it helps, I think ICE should be presented in most simple form.

Output file as shown in first posting.

[ghorrocks]

I don't think an opening BC with flow pulled in can represent piston movement

It is not trying to represent piston movement, so I think you have missed the point of my comment.

I am just suggesting methods of debugging your simulation. The approaches I suggested had one piece of complex physics in it so you could determine what exact bit of physics was having a convergence problem. In your current simulation with everything in it - how can you tell what bit of complex physics is causing the problem?

Once you have found the problematic physics and found a way of getting it to work on a simplified model then you can apply the same approach to the full complex model with some hope that it will work, and some hope that the results will be accurate enough to be useful.

A common newbie mistake is to start a complex new model with everything turned on at once - and then when it inevitably does not work how do you know what the problem is? You develop a complex model one bit of physics at a time, and check that it is working and accurate before working on the next bit of complex physics. Then you can systematically work towards getting your full complex model working.

[visitor]

It's ok G, like most things, will get resolved if you keep at it.

Regarding moving mesh, mesh motion should be sufficient. The moving wall (piston), was defined with motion. Will keep trying, but if there are other specific settings I should know, please let me know, thanks.