Custom field function in CFX

Hunk@cfd · August 9, 2013, 08:03

Hello..I need to calculate the swirl ratio for incylinder motions in CFX. Can anyone help me how to use custom field function in CFX. or Is there any option in CFX like that in FLUENT..Need to submit the project. Kindly help.

ghorrocks · August 9, 2013, 08:22

You can easily write this in CEL, so no need for anything fancy. Use functions like volumeInt() to integrate it over the domain.

Hunk@cfd · August 13, 2013, 17:40

But the formulae for swirl ratio is attached with the post. How do I convert this to CEL format..?..Please help..

ghorrocks · August 13, 2013, 20:26

Your equation for swirl does not look right. If dA means the area integral then it is definitely wrong - swirl is a volume integral thing.

For a correct definition of swirl ratio look at my thesis: http://hdl.handle.net/2100/248, page 74 I think.

This can be implemented as volumeInt(density*r*U)@domain where r and U are displacements and velocities in a cylindrical coord frame around the central axis. You can either calculate these yourself or use a cylidrical frame of reference to get these. I will leave the denominator as an exercise for the reader

.

Hunk@cfd · August 14, 2013, 15:55

If I want to analyse, say the inlet valve is at 2.5mm from TDC, and I want the swirl flow cross sectional view..then area is the required parameter right..? why should I go for volume integral...

Please check the journal prescribed here..

Proceedings of COBEM 2009 20th International Congress of Mechanical Engineering
Copyright © 2009 by ABCM November 15-20, 2009, Gramado, RS, Brazil
DESIGN OF AN INLET TRACK OF A SMALL I. C. ENGINE FOR SWIRL
ENHANCEMENT
Jorge MARTINS, jmartins@dem.uminho.pt
Senhorinha TEIXEIRA, st@dps.uminho.pt
Stijn COENE, stijnxcoene@hotmail.com
Universidade do Minho, Escola de Engenharia, Guimarães, Portugal

ghorrocks · August 14, 2013, 18:50

First of all - there is no universal definition of swirl. People use different definitions. So make sure the definition you intend to use is correct for your application, and when you compare against other people's work ensure they used the same definition of swirl.

Second - I do not have time to read a journal article for you. That is your task, not mine.

Finally - In the page you sent it does not define the dA term. So it is not clear whether it is an area or volume integral. But I would strongly argue against using an area integral as that only gives a swirl number for a single cross section of the flow, not the entire flow.

Hunk@cfd · August 15, 2013, 01:06

Thanks..ghorrocks for your help and valuable comments. I look forward for your help consistently.Thanks a lot..

August 9, 2013, 08:03	Custom field function in CFX	#1
Hunk@cfd New Member praveej Join Date: Jul 2012 Posts: 5 Rep Power: 14	Hello..I need to calculate the swirl ratio for incylinder motions in CFX. Can anyone help me how to use custom field function in CFX. or Is there any option in CFX like that in FLUENT..Need to submit the project. Kindly help.

August 15, 2013, 01:06	Swirl flow	#7
Hunk@cfd New Member praveej Join Date: Jul 2012 Posts: 5 Rep Power: 14	Thanks..ghorrocks for your help and valuable comments. I look forward for your help consistently.Thanks a lot..

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August 9, 2013, 08:22		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	You can easily write this in CEL, so no need for anything fancy. Use functions like volumeInt() to integrate it over the domain.

August 13, 2013, 20:26		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Your equation for swirl does not look right. If dA means the area integral then it is definitely wrong - swirl is a volume integral thing. For a correct definition of swirl ratio look at my thesis: http://hdl.handle.net/2100/248, page 74 I think. This can be implemented as volumeInt(densityrU)@domain where r and U are displacements and velocities in a cylindrical coord frame around the central axis. You can either calculate these yourself or use a cylidrical frame of reference to get these. I will leave the denominator as an exercise for the reader .

August 14, 2013, 18:50		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	First of all - there is no universal definition of swirl. People use different definitions. So make sure the definition you intend to use is correct for your application, and when you compare against other people's work ensure they used the same definition of swirl. Second - I do not have time to read a journal article for you. That is your task, not mine. Finally - In the page you sent it does not define the dA term. So it is not clear whether it is an area or volume integral. But I would strongly argue against using an area integral as that only gives a swirl number for a single cross section of the flow, not the entire flow.