Learning Forum

[Weiqiang Liu]

Hi all,nrecently I've been using fluent to simuation some combustion application with detailed chemical mechanisms. I found inelt condition would influence convergence performance of my case.nFor example, when inlet velocity of fuel air mixture is 0.3, then convergence would be bad and there are unsmooths and flunctuations in profiles report. However, when I increase inlet velocity to 0.5, then resutls are very smooth. The other settigns are just exactly the same. I am wondering why would this happen? why would just inlet velocity influence convergence performance?nBest regardsnweiqiang n

[DrAmine]

Why not: you are basically running a completely different case as you changed the velocity magnitude.n

[Weiqiang Liu]

yes, it's a numeric process. I get it nThanks a lot nweiqiangn

[Rob]

And in a physical sense, lower velocity could promote an unstable jet, large dead zones etc. With combustion you've also then got all the chemistry and burner design:there's a reason most burners have a recommended operating band (pressure/flow & AFR). n

[Weiqiang Liu]

Why not: you are basically running a completely different case as you changed the velocity magnitude.https://forum.ansys.com/discussion/comment/98468#Comment_98468

Hi Dr. Amine,nThanks for reminding. Do you mean in physical world, changing inlet velocity a little bit seems doesn't really change the essence of this problem. However in numerical world, case would iterates very differently with different inlet velocity.nBest regardsnweiqiangn

[Weiqiang Liu]

And in a physical sense, lower velocity could promote an unstable jet, large "dead" zones etc. With combustion you've also then got all the chemistry and burner design: there's a reason most burners have a recommended operating band (pressure/flow & AFR).https://forum.ansys.com/discussion/comment/98476#Comment_98476

Hi Rob,nThanks for sharing me with this konwledge. It's helpful!nBest regardsnweiqiangn