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dandy October 16, 2001 20:18

Convergence when clearance selected

I meet convergence difficulty when clearance selected. I am using CFX-tascflow 2.10. The running problem is an axial compressor which composing twin stage. The problem is easy when clearance didin't select. Then, how can I do when clearance is selected to get a good convergence.Anybody has such experience? Thanks for your help.


Robin Steed October 18, 2001 17:13

Re: Convergence when clearance selected
Hi Dandy,

There is no such selection "clearance" for TASCflow. Do you mean to say that you have created a grid which includes tip clearance? If so, what did you create it in and how did you bring it into TASCflow.

Regards, Robin

dandy October 20, 2001 04:31

Re: Convergence when clearance selected
Thanks Mr. Steed sorry,I forgot it! It is as you said. I create the grid whit tip clearance in use of CFX Turbogrid 1.05. I really met a huge difficulty in running the problem when the grid including a tip clearance. By the way, the grid including tip clearance is as good as the grid without tip clearance in skew! Hoping for your help! thanks

Martin Bowers November 14, 2001 12:06

Re: Convergence when clearance selected
If you are using a GGI clearance template (I suspect you are since you said min skew didn't change when adding clearance) you need to pay particular care to how the clearance grid lines up with the passage grid since the default grid distributions create vastly different spacings on both sides which in turn often cause problems for the GGI.

Check to make sure the clearance GGI has been created in Grid Interfaces. Make sure the initial guess is valid in the clearance region too.

Finally is the case stalled (numerically or physically) with the clearance included? The clearance reduces the stability of the flow and a case that runs with no clearance might not run with clearance for very good reasons.

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