Flow Uniformity Index

fishmonger · November 2, 2015, 12:25

Hello,

I want to plot contour of uniformity index for velocity in CFX-POST.
I did search through the forum and the closest is probably: http://www.cfd-online.com/Forums/cfx...-cfd-post.html

I do not really understand on how to use the polyline and how actually uniformity index contour can be plot from it.

My problem is the same as in this research paper: http://www.sciencedirect.com/science...67610513002857

and particular plot that i want is the "Table 9. Percentage uniformity of flow in test section for the different guide vane configurations" in the paper.

I would be really glad if someone can show me how it can be done.

Thanks
FM

fishmonger · November 2, 2015, 18:53

Really appreciates if anyone could provide the answer.

FM

ghorrocks · November 2, 2015, 20:58

I cannot access your referenced paper.

What is your question? What is a good equation for determining uniformity index; or you already have an equation to define uniformity index and do not know how to implement it?

fishmonger · November 2, 2015, 21:21

i hope this link works for the paper: https://drive.google.com/file/d/0B9L...ew?usp=sharing

My question is, how can i get uniformity index contour for example based on velocity result from CFX-post

and I do not how to implement it in CFX-post and create the contour.

FM

fishmonger · November 2, 2015, 21:27

and I am not sure what is the formula to use.

ghorrocks · November 2, 2015, 21:29

I had a quick look, I could not see how they defined uniformity. But it looks like just the local velocity divided by the average velocity. SO:
* Define a cross section plane
* Define a CEL variable AverageVelocity = massflowAve(u)@plane (it could be u,v or w depending on your orientation)
* Define a variable field VelocityUniformity=u/AverageVelocity
* Draw your cross section plane with VelocityUniformity as the colouring variable.

fishmonger · November 2, 2015, 21:36

* Define a cross section plane: I create a vertical mid plane in my model.

* Define a CEL variable AverageVelocity = massflowAve(u)@plane (it could be u,v or w depending on your orientation): I am not sure how to define the CEL variable. Do i go to variables tab or expression tab to define it?

fishmonger · November 2, 2015, 21:43

sorry again. I am really2 new to CFX expression/variable defination. I hope you can walk the step to me one by one.

Thank you

fishmonger · November 2, 2015, 22:12

ok. I have played around with the expression and variable tab and pretty much know how to do it. thank you so much

Just one more help, Can I specify a specific plane area within a plane section? or specific volume area within the model volume?

Please see the attached file for your reference.

fresty · November 3, 2015, 01:30

You could conveniently specify the plane area while creating the plane.. just play a round a bit in the Plane properties..

fishmonger · November 3, 2015, 02:15

Yup fresty or I can defined an iso-plane

Thanks Everyone

ghorrocks · November 3, 2015, 03:46

From your image of your simulation I can see your mesh is far too coarse for anything approaching accurate results. Your results form this model is bound to be highly inaccurate. You will need to refine the mesh and do a mesh sensitivity study if you want reasonable results.

November 2, 2015, 12:25	Flow Uniformity Index	#1
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	Hello, I want to plot contour of uniformity index for velocity in CFX-POST. I did search through the forum and the closest is probably: http://www.cfd-online.com/Forums/cfx...-cfd-post.html I do not really understand on how to use the polyline and how actually uniformity index contour can be plot from it. My problem is the same as in this research paper: http://www.sciencedirect.com/science...67610513002857 and particular plot that i want is the "Table 9. Percentage uniformity of flow in test section for the different guide vane configurations" in the paper. I would be really glad if someone can show me how it can be done. Thanks FM

November 2, 2015, 22:12		#9
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	ok. I have played around with the expression and variable tab and pretty much know how to do it. thank you so much Just one more help, Can I specify a specific plane area within a plane section? or specific volume area within the model volume? Please see the attached file for your reference. Last edited by fishmonger; November 3, 2015 at 10:55.

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November 2, 2015, 18:53		#2
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	Really appreciates if anyone could provide the answer. FM

November 2, 2015, 20:58		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	I cannot access your referenced paper. What is your question? What is a good equation for determining uniformity index; or you already have an equation to define uniformity index and do not know how to implement it?

November 2, 2015, 21:21		#4
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	i hope this link works for the paper: https://drive.google.com/file/d/0B9L...ew?usp=sharing My question is, how can i get uniformity index contour for example based on velocity result from CFX-post and I do not how to implement it in CFX-post and create the contour. FM

November 2, 2015, 21:27		#5
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	and I am not sure what is the formula to use.

November 2, 2015, 21:29		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	I had a quick look, I could not see how they defined uniformity. But it looks like just the local velocity divided by the average velocity. SO: * Define a cross section plane * Define a CEL variable AverageVelocity = massflowAve(u)@plane (it could be u,v or w depending on your orientation) * Define a variable field VelocityUniformity=u/AverageVelocity * Draw your cross section plane with VelocityUniformity as the colouring variable.

November 2, 2015, 21:36		#7
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	* Define a cross section plane: I create a vertical mid plane in my model. * Define a CEL variable AverageVelocity = massflowAve(u)@plane (it could be u,v or w depending on your orientation): I am not sure how to define the CEL variable. Do i go to variables tab or expression tab to define it?

November 2, 2015, 21:43		#8
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	sorry again. I am really2 new to CFX expression/variable defination. I hope you can walk the step to me one by one. Thank you

November 3, 2015, 01:30		#10
fresty Senior Member Join Date: Aug 2014 Location: UK Posts: 213 Rep Power: 12	You could conveniently specify the plane area while creating the plane.. just play a round a bit in the Plane properties..

November 3, 2015, 02:15		#11
fishmonger New Member Join Date: Oct 2015 Posts: 8 Rep Power: 10	Yup fresty or I can defined an iso-plane Thanks Everyone

November 3, 2015, 03:46		#12
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	From your image of your simulation I can see your mesh is far too coarse for anything approaching accurate results. Your results form this model is bound to be highly inaccurate. You will need to refine the mesh and do a mesh sensitivity study if you want reasonable results.