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Old   June 20, 2014, 04:29
Default Accessing cell values (CFX Pre and CFX Post)
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Hi,

Is it possible to write an expression which needs variable's value in each cell in CFX Pre?

Also, would it be possible to access any variable's value cell wise in CFD Post?

If yes, plz suggest me some links or documents.

Thanks
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Old   June 20, 2014, 05:36
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i dont think so.there is new futures in ansys v15 that makes it possible to observe and call parameters in elements but i have not tried it yet
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Old   June 20, 2014, 07:25
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Quote:
Originally Posted by hmasenger View Post
i dont think so.there is new futures in ansys v15 that makes it possible to observe and call parameters in elements but i have not tried it yet

could you plz elaborate a little bit about the v15 feature you are talking about? and whether it is available in CFD Post documentation?
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Old   June 21, 2014, 14:47
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Take a look at ansys.com ir google it;-)
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Old   June 22, 2014, 07:13
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brahmarishiraj:

Any CEL expression on a field variable is calculated per control volume. So it accesses the variable's value is every cell. Alternately the point() CEL expression can extract values at specific points.

But I do not know what you are trying to do so say whether this is relevant or not.
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Old   June 22, 2014, 23:22
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Quote:
Originally Posted by ghorrocks View Post
brahmarishiraj:

Any CEL expression on a field variable is calculated per control volume. So it accesses the variable's value is every cell. Alternately the point() CEL expression can extract values at specific points.

But I do not know what you are trying to do so say whether this is relevant or not.
Dear Glen,

thanks for the comments.
In my modeling there are droplets. I have to write some expressions where I need droplet dia in each cell. Could you please suggest how cells are numbered or how can I access them?

Thanks
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Old   June 22, 2014, 23:50
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How are you modelling the droplet? Eularian or lagrangian? If eularian then are you using a free surface model or a droplet model?

Do not jump to the conclusion that you need to know how the cells are numbered - with the way CEL works in CFX you probably do not need to do anything at that level. It probably cal be done as a simple CEL expression.
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Old   June 22, 2014, 23:52
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Quote:
Originally Posted by ghorrocks View Post
How are you modelling the droplet? Eularian or lagrangian? If eularian then are you using a free surface model or a droplet model?

Do not jump to the conclusion that you need to know how the cells are numbered - with the way CEL works in CFX you probably do not need to do anything at that level. It probably cal be done as a simple CEL expression.
I am using Lagrangian.
May be this would help you to answer better.
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Old   June 22, 2014, 23:57
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Have a look in the CFX reference manual, section 16.3.2.3.

The following variables exist for lagrangian simulations:
Averaged Mean Particle Diameter
Averaged Arithmetic Mean Particle Diameter
Averaged Surface Mean Particle Diameter
Averaged Volume Mean Particle Diameter
Averaged Sauter Mean Particle Diameter
Averaged Mass Mean Particle Diameter

So the diameter you are looking for looks like it already exists in CEL.
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Old   June 23, 2014, 00:02
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Quote:
Originally Posted by ghorrocks View Post
Have a look in the CFX reference manual, section 16.3.2.3.

The following variables exist for lagrangian simulations:
Averaged Mean Particle Diameter
Averaged Arithmetic Mean Particle Diameter
Averaged Surface Mean Particle Diameter
Averaged Volume Mean Particle Diameter
Averaged Sauter Mean Particle Diameter
Averaged Mass Mean Particle Diameter

So the diameter you are looking for looks like it already exists in CEL.
Glen,

I agree with you that it is there, I had seen that before posting as you always mention to do.
But can I get the values in each cell?
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Old   June 23, 2014, 00:47
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If you do a CEL expression with field variables it will return a variable field.

If you explained what you are trying to do maybe we can help you better.
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Old   June 24, 2014, 02:33
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Quote:
Originally Posted by ghorrocks View Post
If you do a CEL expression with field variables it will return a variable field.

If you explained what you are trying to do maybe we can help you better.

Thanks Glen for the help.

I have a paper which tells how to calculate the efficiency of the scrubber empirically, I don't know how to implement in CFX.

I have attached the equation part here,
Plz guide.
Attached Files
File Type: docx Efficiency of Venturi.docx (49.8 KB, 3 views)
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Old   June 24, 2014, 02:58
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This is easy to write in CEL.

u is Gas_Phase.velocity (assuming the gas phase is a continuous phase)
v is droplet_phase.Averaged Velocity (assuming the droplet phase is a lagrangian phase)
rho is dust.Dust_Density (assuming lagrangian, and use this CEL variable to set the dust phase density)
mu is Gas_Phase.viscosity
diameters are described in the CFX reference guide - you get the idea, I trust.
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Old   June 24, 2014, 03:07
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Quote:
Originally Posted by ghorrocks View Post
This is easy to write in CEL.

u is Gas_Phase.velocity (assuming the gas phase is a continuous phase)
v is droplet_phase.Averaged Velocity (assuming the droplet phase is a lagrangian phase)
rho is dust.Dust_Density (assuming lagrangian, and use this CEL variable to set the dust phase density)
mu is Gas_Phase.viscosity
diameters are described in the CFX reference guide - you get the idea, I trust.

Glen,

My doubt is- as there is a distribution/spectrum of diameter of droplet, which one should be considered? Also the velocity changes along the length, so at which cross section or which velocity shall i consider?

That's why I wanted to this equation in such a way that this parameter gets calculated for each cell.

Any further suggestions?
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Old   June 24, 2014, 19:12
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The variables I mentioned are control volume variables or particle variables.

Can you specify exactly what equation you are trying to implement? Please define which variables are local and which are averaged, and if averaged where the average is taken from.
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