Segregated Vs Coupled Solvers

Bal21 · May 29, 2022, 14:59

Hi all,

When I use K- omega SST and a segregated solver, the simulation works fine,, but the value is much lower than the experimental one.

When I switch to coupled solver, the simulation terminates early at iteration 68.

What is the likelihood that the segregated solver is less accurate than coupled? I tried communicating with the support, but they weren't helpful.

Appreciate your prompt responses

Thanks!
Bal

LuckyTran · May 31, 2022, 00:13

If your simulation crashes at iteration 68 then you have a convergence problem and you need help setting up your simulation. Accuracy is a different concern altogether.

Bal21 · May 31, 2022, 01:27

But it converged using the segregated solver. The divergence occured only using the coupled solver... what would that mean?

LuckyTran · May 31, 2022, 08:15

It just means it diverged because you didn't do a good enough job in setting up the simulation. Not all solvers and all settings are guaranteed to converge every time. Just do a better job.

Bal21 · May 31, 2022, 08:50

Haha
Thank you

Nikpap · June 8, 2022, 10:34

There are a couple of threads here about your problem:

Segregated or Coupled flow?

and

Segregated vs Coupled Solver

May 29, 2022, 14:59	Segregated Vs Coupled Solvers	#1
Bal21 Member Bal Join Date: Nov 2021 Posts: 49 Rep Power: 4	Hi all, When I use K- omega SST and a segregated solver, the simulation works fine,, but the value is much lower than the experimental one. When I switch to coupled solver, the simulation terminates early at iteration 68. What is the likelihood that the segregated solver is less accurate than coupled? I tried communicating with the support, but they weren't helpful. Appreciate your prompt responses Thanks! Bal

June 8, 2022, 10:34		#6
Nikpap New Member Nikolaos Papafilippou Join Date: Apr 2019 Posts: 25 Rep Power: 7	There are a couple of threads here about your problem: Segregated or Coupled flow? and Segregated vs Coupled Solver allanZHONG, Bal21 and chencfd like this.

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May 31, 2022, 00:13		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	If your simulation crashes at iteration 68 then you have a convergence problem and you need help setting up your simulation. Accuracy is a different concern altogether.

May 31, 2022, 01:27		#3
Bal21 Member Bal Join Date: Nov 2021 Posts: 49 Rep Power: 4	But it converged using the segregated solver. The divergence occured only using the coupled solver... what would that mean?

May 31, 2022, 08:15		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	It just means it diverged because you didn't do a good enough job in setting up the simulation. Not all solvers and all settings are guaranteed to converge every time. Just do a better job.

May 31, 2022, 08:50		#5
Bal21 Member Bal Join Date: Nov 2021 Posts: 49 Rep Power: 4	Haha Thank you