[ICEM] Will grid independency for one fluid be valid for any other?

Shomaz ul Haq · June 7, 2017, 01:35

Dear all. Hello. Hope all are well. I have a question. This may seem a very simple question but I really don't know the answer. Will grid independency for one fluid (e.g. water) in a closed flow model be valid for any other fluid? Would be grateful for help. Thanks.

Kina · June 7, 2017, 04:50

I am almost 100% sure that it will not be applicable. The grid independency is based on the theory that your mesh is fine enough to resolve every physics the model is able to capture. In case of another fluid you might have different turbulence scales and therefore you may need a different mesh resolution.

Shomaz ul Haq · June 7, 2017, 04:59

Thank you Alex. You are most probably right. But then why do I see people applying grid refinement for one fluid (water in many cases) and then applying other fluids for the same model keeping everything else the same in research articles. I don't get this. It is strange. Also you talked about different turbulence scales but my model is laminar. How would turbulence scales affect my grid independency? Hope you can shed some light on these two questions. Hope to hear from other seniors on this matter too. Would be grateful. Thanks.

Shomaz ul Haq · June 9, 2017, 02:06

Dear all,

Hello. Hope everyone is great. Hope somebody could give an explanation to my last questions posted earlier. Would be grateful from some advice from senior experts. Thanks.

Shomaz ul Haq · June 12, 2017, 02:54

Dear all,

Hello. Hope all are well. Can anybody help me out with my questions in this thread? Would be extremely grateful. Thanks.

BlnPhoenix · June 12, 2017, 03:20

I agree with Alex that one should do a grid refinement study when changing the working fluid, because with the fluid the fluid dynamics change. BUT if the fluid has nearly similar properties one could make the assumption that the same grid is equally good.

So it would be simply a matter of time/cost saving. From my experience in practice it is already hard enough to convince the decision makers to do grid refinement studies AT ALL.

Shomaz ul Haq · June 12, 2017, 07:06

Thanks a lot BlnPhoenix. I get it now.

June 7, 2017, 01:35	Will grid independency for one fluid be valid for any other?	#1
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 11	Dear all. Hello. Hope all are well. I have a question. This may seem a very simple question but I really don't know the answer. Will grid independency for one fluid (e.g. water) in a closed flow model be valid for any other fluid? Would be grateful for help. Thanks.

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June 7, 2017, 04:50		#2
Kina Senior Member Alex Join Date: Jan 2014 Posts: 126 Rep Power: 12	I am almost 100% sure that it will not be applicable. The grid independency is based on the theory that your mesh is fine enough to resolve every physics the model is able to capture. In case of another fluid you might have different turbulence scales and therefore you may need a different mesh resolution.

June 7, 2017, 04:59		#3
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 11	Thank you Alex. You are most probably right. But then why do I see people applying grid refinement for one fluid (water in many cases) and then applying other fluids for the same model keeping everything else the same in research articles. I don't get this. It is strange. Also you talked about different turbulence scales but my model is laminar. How would turbulence scales affect my grid independency? Hope you can shed some light on these two questions. Hope to hear from other seniors on this matter too. Would be grateful. Thanks.

June 9, 2017, 02:06		#4
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 11	Dear all, Hello. Hope everyone is great. Hope somebody could give an explanation to my last questions posted earlier. Would be grateful from some advice from senior experts. Thanks.

June 12, 2017, 02:54		#5
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 11	Dear all, Hello. Hope all are well. Can anybody help me out with my questions in this thread? Would be extremely grateful. Thanks.

June 12, 2017, 03:20		#6
BlnPhoenix Senior Member Join Date: Aug 2014 Location: Germany Posts: 292 Rep Power: 13	I agree with Alex that one should do a grid refinement study when changing the working fluid, because with the fluid the fluid dynamics change. BUT if the fluid has nearly similar properties one could make the assumption that the same grid is equally good. So it would be simply a matter of time/cost saving. From my experience in practice it is already hard enough to convince the decision makers to do grid refinement studies AT ALL.

June 12, 2017, 07:06		#7
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 11	Thanks a lot BlnPhoenix. I get it now.