mixing tank

wemendibe · June 22, 2013, 13:29

If I put 100 rpm rotational velocity to the impeller in the mixing tank it converge, but if I put 500 rpm it does not converge, do anyone knows why??
I put in viscous model k-epsilon RNG, because it is turbulent, I can say if anyone knows all the steps that I have.

Thank you

Mikel Mendibe

Far · June 23, 2013, 04:27

At off-design conditions you will have more separation and hence difficulty in converging steady state solution.

wemendibe · June 23, 2013, 05:19

So, do you mean that is normal to do not convege?

Far · June 23, 2013, 06:16

yes, if it is not a design condition. At off design conditions you may need to activate unsteady flow solver.

wemendibe · June 23, 2013, 06:32

Thank you. I have another question, I want that the wall of the tank heat the fuild that I have. I go to the wall and I put the temperature that I want, is it ok?

Thank you

Far · June 23, 2013, 06:39

yes. Also enable energy equation.

A CFD free user · June 25, 2013, 03:22

You should increase the impeller speed gradually untill to reach your desire speed. For instance, to do a simulation with 400 rpm, first start with 100, then increase it about 20 rpm and go ahead. once I had the same problem too. Try this it helps.

June 22, 2013, 13:29	mixing tank	#1
wemendibe New Member Mikel Mendibe Join Date: Mar 2013 Posts: 23 Rep Power: 13	If I put 100 rpm rotational velocity to the impeller in the mixing tank it converge, but if I put 500 rpm it does not converge, do anyone knows why?? I put in viscous model k-epsilon RNG, because it is turbulent, I can say if anyone knows all the steps that I have. Thank you Mikel Mendibe

June 25, 2013, 03:22		#7
A CFD free user Senior Member A-A Azarafza Join Date: Jan 2013 Posts: 226 Rep Power: 14	You should increase the impeller speed gradually untill to reach your desire speed. For instance, to do a simulation with 400 rpm, first start with 100, then increase it about 20 rpm and go ahead. once I had the same problem too. Try this it helps. __________________ Regard yours

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June 23, 2013, 04:27		#2
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	At off-design conditions you will have more separation and hence difficulty in converging steady state solution.

June 23, 2013, 05:19		#3
wemendibe New Member Mikel Mendibe Join Date: Mar 2013 Posts: 23 Rep Power: 13	So, do you mean that is normal to do not convege?

June 23, 2013, 06:16		#4
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	yes, if it is not a design condition. At off design conditions you may need to activate unsteady flow solver.

June 23, 2013, 06:32		#5
wemendibe New Member Mikel Mendibe Join Date: Mar 2013 Posts: 23 Rep Power: 13	Thank you. I have another question, I want that the wall of the tank heat the fuild that I have. I go to the wall and I put the temperature that I want, is it ok? Thank you

June 23, 2013, 06:39		#6
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	yes. Also enable energy equation.