CFD Online Logo CFD Online URL
Home > Forums > CFX

CFX Parallel

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   October 15, 2014, 07:53
Default CFX Parallel
New Member
Join Date: Oct 2014
Posts: 2
Rep Power: 0
ihsb is on a distinguished road

I have observed a problem running CFX V15.0 parallel that I can't explain.

The problem I am trying to calculate is an axial turbine. The geometry is build up with one guide vane passage one runner passage and a full 360-draft tube with an artificial extension. The simulation is performed steady state with an physical time scale which would correspond to 5 runner revolution. Stage interfaces are used between the rotor and the stator.

When running serial the simulation is running without any problems. It is also possible to run the simulation on 4 cores parallel without any problems.

The problem appears if one wants to increase the amount of parallel partitions the run. The run is aborting after a couple of iterations with an overflow.
In the out-file it can be seen that the solver has placed 100% wall at the outlet.

I tied the following ways to solve the problem:
1) Putting an opening boundary condition at the outflow
2) Increasing and decreasing the time step
3) Starting the run from an initial result file, computed on less cores
4) Using a full 360-geometry of guide vane and runner (with stage interface)
5) Running a full 360 transient simulation (with transient interfaces between the rotor stator domains) with different time step sizes
6) Using CFX 14.5 for the steady state simulations.

All the mentioned approaches didn't solve the problem. To be honest I actually don't know what else I can try to solve the problem. Does anyone have an advice how to solve the problem?

ihsb is offline   Reply With Quote

Old   October 15, 2014, 17:12
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 14,101
Rep Power: 109
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
Try different partitioning methods.

Also, you have forgotten to try the most important thing when dealing with numerical difficulties - improve the mesh quality.
And double precision numerics are worth a try as well.
ghorrocks is offline   Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Parallel Problem of CFX 14.5.7 on a Intel Xeon 2690V2 computer with Win7 x64 OS BruceWen CFX 14 September 16, 2014 19:25
Parallel Problem of CFX 14.5.7 on a Intel Xeon 2690V2 computer with Win7 x64 OS BruceWen Hardware 0 April 29, 2014 23:48
RSH on Windows for CFX parallel computation BalanceChen CFX 3 June 15, 2012 12:34
CFX parallel multi-node jobs fail w/ SLURM on Ubuntu 10.04 danieru CFX 0 February 17, 2012 07:20
CFX 13 Linux (Ubuntu 11.10) local parallel setup TSokl ANSYS 0 January 16, 2012 08:35

All times are GMT -4. The time now is 19:39.