convergence and conservation target of h-energy euqation

gitsnedbutzi · April 19, 2011, 10:50

Hi,

I have a simulation consisting of two domains, a fluid and solid one.
However, I am struggling to achieve convergence to a residual of 1e-5 during the steady state simulation, which should be the starting point for a transient simulation.

During the transient simulation, I achieve convergence but not the conservation target of 1%. The imbalance is about 1,5%.

So far I have been struggling to achieve both targets. Any ideas on how to improve convergence and achieve the conservation target would be greatly appreciated!!

Thanks

ghorrocks · April 19, 2011, 22:24

CHT simulations often like a generous solid time scale factor. This advances time in the solid region faster than the fluid region as the time scales in the solid region are usually far slower than the fluid time scales.

gitsnedbutzi · April 20, 2011, 14:41

thanks, i wouldnt be worried if the convergence is slower. however the residual stagnates and doesnt converge at all. aren't there options for the solver / preconditioner that help. the only thing i have seen is the time scale factor, but it doesnt help.

ghorrocks · April 20, 2011, 19:58

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

April 19, 2011, 10:50	convergence and conservation target of h-energy euqation	#1
gitsnedbutzi New Member name Join Date: Mar 2009 Posts: 9 Rep Power: 17	Hi, I have a simulation consisting of two domains, a fluid and solid one. However, I am struggling to achieve convergence to a residual of 1e-5 during the steady state simulation, which should be the starting point for a transient simulation. During the transient simulation, I achieve convergence but not the conservation target of 1%. The imbalance is about 1,5%. So far I have been struggling to achieve both targets. Any ideas on how to improve convergence and achieve the conservation target would be greatly appreciated!! Thanks

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April 19, 2011, 22:24		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	CHT simulations often like a generous solid time scale factor. This advances time in the solid region faster than the fluid region as the time scales in the solid region are usually far slower than the fluid time scales.

April 20, 2011, 14:41		#3
gitsnedbutzi New Member name Join Date: Mar 2009 Posts: 9 Rep Power: 17	thanks, i wouldnt be worried if the convergence is slower. however the residual stagnates and doesnt converge at all. aren't there options for the solver / preconditioner that help. the only thing i have seen is the time scale factor, but it doesnt help.

April 20, 2011, 19:58		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	http://www.cfd-online.com/Wiki/Ansys...gence_criteria