Time step and Courant in Coupled

Alberto Damas · April 5, 2019, 09:12

Hi,

I want to use the coupled solver but I don't know why can I define both Courant number and time step since they are basically the same. How does it work? Does Fluent solve internally more time steps to accomplish the CFL condition? If so, is there any rule to find the best combination of them in terms of computational time?

I've been searching information about it but I haven't found a clear answer.

Thx for answering

LuckyTran · April 5, 2019, 10:54

Because it's not Courant number but "Flow Courant number." Funny how the human mind can completely ignore words... =)

The time-step size is still the time-step size. The "Flow Courant number" setting is analogous to an implicit under-relaxation factor. Set it to infinity for no underelaxation.

It's actually fairly well explained in the Fluent manual but you need to look for "Flow Courant number" and not confuse this with "Courant number"

Alberto Damas · April 8, 2019, 06:07

Hi,

thank you for answering, you helped me a lot.

April 5, 2019, 09:12	Time step and Courant in Coupled	#1
Alberto Damas Member Alberto Join Date: Aug 2015 Posts: 31 Rep Power: 10	Hi, I want to use the coupled solver but I don't know why can I define both Courant number and time step since they are basically the same. How does it work? Does Fluent solve internally more time steps to accomplish the CFL condition? If so, is there any rule to find the best combination of them in terms of computational time? I've been searching information about it but I haven't found a clear answer. Thx for answering

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April 5, 2019, 10:54		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,676 Rep Power: 66	Because it's not Courant number but "Flow Courant number." Funny how the human mind can completely ignore words... =) The time-step size is still the time-step size. The "Flow Courant number" setting is analogous to an implicit under-relaxation factor. Set it to infinity for no underelaxation. It's actually fairly well explained in the Fluent manual but you need to look for "Flow Courant number" and not confuse this with "Courant number"

April 8, 2019, 06:07		#3
Alberto Damas Member Alberto Join Date: Aug 2015 Posts: 31 Rep Power: 10	Hi, thank you for answering, you helped me a lot.