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Old   August 22, 2005, 09:54
Default Convergence issues
  #1
derick
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Dear all:

I was trying to model a pretty huge pipe with lots of bends and all and with an inlet velocity of 27 m/s. the total span of the pipe on x dir would be around 10m and y would be around the same. i was trying to model a part of a pipe in a power plant. the problem was that i was getting divergence when i used an unsteady implicit solver..any thoughts...or is it just that the whole system is just very unstable one??

thanks in advance
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Old   August 22, 2005, 10:44
Default Re: Convergence issues
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swarup
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this will need very good mesh i guess. i will say system is quite wild!
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Old   August 22, 2005, 14:08
Default Re: Convergence issues
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Masood
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hi derick i think u dont have to model the whole pipe at same time. try model a type of geometry (means pipe of certain dia with certain bend angle)one by one. and for similar type just add the losses etc.

i hope i made my point clear.(divide and rule)
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Old   August 22, 2005, 14:57
Default Re: Convergence issues
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helper
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Try one or all of these to see if it works - smaller time-step size, smaller under-relaxation factors (segregated solver) or CFL number (coupled solver).
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Old   August 22, 2005, 15:09
Default Re: Convergence issues
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derick
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thanks guys for ur help..i will surely try all ur suggestions. hope they work...thanks once again guys
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