How to define the values of k and epsilon in pimplefoam?

mo___ · April 18, 2024, 10:42

Hi all,

I'm new to turbuluence modeling and not sure how I should specify the values of k and epsilon in zero directory for the problem I'm trying to simulate. I'm trying to simulate a mixing process in a micromixer device but when i put the values of k and epsilon close to zero ( since I initilize the flow field with zero velocity) the simulation crashes but when i put the values equal to 1, it converges. However, when I increase the value of velocity for analyzing higher Reynolds number, my simulation crashes again even with k and epsilon = 1. So I was wondering how I should define these values and whether I need to change them case by case if I change the velocity magnitude?

Thanks so much for your help.

determinant · August 31, 2024, 08:39

when you put k values 1, what k values did you get after run?

CFD_with_Skill-Lync · October 8, 2024, 07:59

Hi,

You can use an online calculator for approximate values for starting the simulation. Notably, CFD Online has its own turbulence calculator (https://www.cfd-online.com/Tools/tur...eat-exchangers)

Check with literature about what exactly is the turbulence intensity % being used for your case setup, and follow the same.

Please reach out in case you have any questions regarding this.

Team Skill-Lync

April 18, 2024, 10:42	How to define the values of k and epsilon in pimplefoam?	#1
mo___ New Member mo magd Join Date: Apr 2024 Posts: 7 Rep Power: 2	Hi all, I'm new to turbuluence modeling and not sure how I should specify the values of k and epsilon in zero directory for the problem I'm trying to simulate. I'm trying to simulate a mixing process in a micromixer device but when i put the values of k and epsilon close to zero ( since I initilize the flow field with zero velocity) the simulation crashes but when i put the values equal to 1, it converges. However, when I increase the value of velocity for analyzing higher Reynolds number, my simulation crashes again even with k and epsilon = 1. So I was wondering how I should define these values and whether I need to change them case by case if I change the velocity magnitude? Thanks so much for your help.

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August 31, 2024, 08:39		#2
determinant New Member BK Join Date: Jan 2024 Posts: 2 Rep Power: 0	when you put k values 1, what k values did you get after run?

October 8, 2024, 07:59		#3
CFD_with_Skill-Lync New Member Skill-Lync CFD Join Date: Sep 2024 Location: Chennai Posts: 18 Rep Power: 2	Hi, You can use an online calculator for approximate values for starting the simulation. Notably, CFD Online has its own turbulence calculator (https://www.cfd-online.com/Tools/tur...eat-exchangers) Check with literature about what exactly is the turbulence intensity % being used for your case setup, and follow the same. Please reach out in case you have any questions regarding this. Team Skill-Lync