Help with tke and sdr convergence

rouco75 · May 22, 2020, 18:38

Hello everyone,

I am having a little problem, I have tweaked the relaxation factors following the rule of adding 1 between pressure and velocity and I was getting good results, but now in a new simulation I am getting divergent turbulence sdr and tke after 1000 iterations.

Does anyone know why is this happening? It is not a problem of geometry as it has been prepared for CFD and the mesh is as good as it can be taking into account the computational resources.

Here you can see what I mean by the residuals diverging.

qin chunqiu · May 23, 2020, 03:31

more details needed

rouco75 · May 23, 2020, 22:07

What kind of details? The physics model used is an SST k-w gamma transition, it is segregated flow where the relaxation factor of velocity goes from 0.8 to 0.2 linearly and the opposite for the pressure (i.e. from 0.2 to 0.8). [This gave me quite good stability and steady forces]. Don't know what else can I say about it, mesh is good, y+ below 1, growth factors are 1.1 or less..., geometry is healed...

qin chunqiu · May 26, 2020, 04:51

Quote:

Originally Posted by rouco75

What kind of details? The physics model used is an SST k-w gamma transition, it is segregated flow where the relaxation factor of velocity goes from 0.8 to 0.2 linearly and the opposite for the pressure (i.e. from 0.2 to 0.8). [This gave me quite good stability and steady forces]. Don't know what else can I say about it, mesh is good, y+ below 1, growth factors are 1.1 or less..., geometry is healed...

Well, a finer mesh maybe help. From your residual plots, the convergence is not so good even in the first 600 iterations.

Lijo Joseph · February 22, 2022, 00:20

Hi, did you find the reason for convergence?

azt · May 13, 2022, 04:47

How do you know that your flow is transitional?

azt

May 22, 2020, 18:38	Help with tke and sdr convergence	#1
rouco75 New Member Adrian Rouco Join Date: Mar 2018 Posts: 13 Rep Power: 8	Hello everyone, I am having a little problem, I have tweaked the relaxation factors following the rule of adding 1 between pressure and velocity and I was getting good results, but now in a new simulation I am getting divergent turbulence sdr and tke after 1000 iterations. Does anyone know why is this happening? It is not a problem of geometry as it has been prepared for CFD and the mesh is as good as it can be taking into account the computational resources. Here you can see what I mean by the residuals diverging.

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May 23, 2020, 03:31		#2
qin chunqiu New Member Join Date: Sep 2010 Location: Wuhan, China Posts: 23 Rep Power: 15	more details needed

May 23, 2020, 22:07		#3
rouco75 New Member Adrian Rouco Join Date: Mar 2018 Posts: 13 Rep Power: 8	What kind of details? The physics model used is an SST k-w gamma transition, it is segregated flow where the relaxation factor of velocity goes from 0.8 to 0.2 linearly and the opposite for the pressure (i.e. from 0.2 to 0.8). [This gave me quite good stability and steady forces]. Don't know what else can I say about it, mesh is good, y+ below 1, growth factors are 1.1 or less..., geometry is healed...

February 22, 2022, 00:20		#5
Lijo Joseph New Member Lijo Join Date: Feb 2022 Posts: 1 Rep Power: 0	Hi, did you find the reason for convergence?

May 13, 2022, 04:47		#6
azt Member allan thomson Join Date: Mar 2009 Location: scotland Posts: 45 Rep Power: 17	How do you know that your flow is transitional? azt