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-   -   residual oscillations (https://www.cfd-online.com/Forums/cfx/85321-residual-oscillations.html)

cfdgalaxy February 23, 2011 03:05

residual oscillations
 
hi im relatively new to cfx, and im trying to model a can combustor flow with a mixture of propane and butane as the fuel. im getting steady residual oscillations in the solver after a 100 hundred iterations. im using EDM, k-e for turbulence. can anyone tell me why this is happening - i've tried changing to physical timescale, increasing the timestep, decreasing it,but nothing is working.:confused: id be really grateful for any help. thanks.

ghorrocks February 23, 2011 17:45

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

joey2007 February 24, 2011 14:43

Did it converge without combustion?
What does the mesh quality report in the outfile say?

cfdgalaxy February 28, 2011 02:34

@ghorrocks, i ve read through that already.. and though the timescale alteration works for some curves, the others are still steadily in a straight line. is it possible i have to change my boundary conditions? i have converged similar models with the same BCs.
@joey: i havent tried running it without combustion. i will do that now and see.

cfdgalaxy February 28, 2011 07:36

it doesnt converge without combustion either - what does that mean?

ghorrocks February 28, 2011 17:42

Quote:

and though the timescale alteration works for some curves
The page I referenced discusses a lot more than just the time scale. If the timescale does not work you have to consider the other approaches discussed there.

joey2007 March 1, 2011 15:25

If it does not converge without combustion, something basic is wrong. Follow the recommendation from Glenn.


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