How to make Nussel Number Contours in ANSYS CFX?

AliM123 · October 25, 2020, 04:10

Hi Everyone
I am working on Gas Turbine Blade. I want to know that how to make Nusselt Number Contours in CFX Post.

Thanks

ghorrocks · October 25, 2020, 17:12

Define a user variable (Variables tab, right click "New") and define a CEL expression which gives your definition of Nusselt Number. It will then appear as a variable which can be used for contours, streamlines, isosurfaces and all the other functions.

Note that Nusselt number takes the heat transfer at a boundary, so it is only defined at a boundary. This means only post-processing objects which work on boundary surfaces will be able to show it, such as contours. Post processing objects which work on the 3D domain (such as streamlines or cross section planes) will not show it.

AliM123 · October 29, 2020, 08:07

Thank you for your reply.

I have a problem when I create the expression then there is some kind of error shown that is "Reference error".

How to create reference in ANSYS CFX?

Regards

Gert-Jan · October 29, 2020, 08:49

This doesn't ring a bell.
Where did the error occur? In Pre? Then cut and paste the error here, or make a screenshot.

AliM123 · November 2, 2020, 02:29

In my case, there is a hot domain, cold domain, and Aluminum solid blade.

Hot Fluid Temperature is 296K
Cold Fluid Temperature is 296K
Internal Surface Heat Flux is 2000(W/m2-K)

Gert-Jan · November 2, 2020, 02:34

This has nothing to do with 'reference'.
In your Nu-equations, you use the term 'Twall'.
But since you haven't defined what Twall is, CFX gives this error.
Probably you need to define something like: Twall = areaAve(T)@Wall

AliM123 · November 2, 2020, 02:47

The temperature of the wall is defined as automatic in CFX Pre.

AliM123 · November 2, 2020, 02:58

Same error again.

I want to know that is there any line or point to define this reference on the blade surface?

And how to define this?

Gert-Jan · November 2, 2020, 03:11

You should do some more tutorials since you are missing some basic knowledge of CFX.

Gert-Jan · November 2, 2020, 03:13

Quote:

Originally Posted by AliM123

The temperature of the wall is defined as automatic in CFX Pre.

This is about initialization. Besides setting the temperature everywhere on the first iteration, this has nothing to do with the temperature on the wall.

AliM123 · November 3, 2020, 07:46

Thank you for your guidance. The issue is resolved but I want to create Nusselt Number Contours as shown in the attached picture.

How to make Nusselt number contour on the curve body?

ghorrocks · November 3, 2020, 16:37

You should do the CFX tutorials. This is a really basic question.

You just define a contour object and define the surface you want as the location.

October 25, 2020, 04:10	How to make Nussel Number Contours in ANSYS CFX?	#1
AliM123 New Member Ali M Join Date: Oct 2020 Posts: 6 Rep Power: 5	Hi Everyone I am working on Gas Turbine Blade. I want to know that how to make Nusselt Number Contours in CFX Post. Thanks

October 25, 2020, 17:12		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	Define a user variable (Variables tab, right click "New") and define a CEL expression which gives your definition of Nusselt Number. It will then appear as a variable which can be used for contours, streamlines, isosurfaces and all the other functions. Note that Nusselt number takes the heat transfer at a boundary, so it is only defined at a boundary. This means only post-processing objects which work on boundary surfaces will be able to show it, such as contours. Post processing objects which work on the 3D domain (such as streamlines or cross section planes) will not show it. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

November 3, 2020, 16:37		#12
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	You should do the CFX tutorials. This is a really basic question. You just define a contour object and define the surface you want as the location. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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October 29, 2020, 08:07		#3
AliM123 New Member Ali M Join Date: Oct 2020 Posts: 6 Rep Power: 5	Thank you for your reply. I have a problem when I create the expression then there is some kind of error shown that is "Reference error". How to create reference in ANSYS CFX? Regards

October 29, 2020, 08:49		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	This doesn't ring a bell. Where did the error occur? In Pre? Then cut and paste the error here, or make a screenshot.

November 2, 2020, 02:34		#6
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	This has nothing to do with 'reference'. In your Nu-equations, you use the term 'Twall'. But since you haven't defined what Twall is, CFX gives this error. Probably you need to define something like: Twall = areaAve(T)@Wall

November 2, 2020, 03:11		#9
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	You should do some more tutorials since you are missing some basic knowledge of CFX.