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Old   August 24, 2008, 21:55
Default New Variable in CFX Post
  #1
Ben
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Hi,

I'm trying to create a new vector variable in CFX post. (velocity * vorticity). However, I can't get to assign the new variables. Does anyone know how to assign a new variable dependent on existing variables?

Cheers, ben
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Old   August 24, 2008, 22:35
Default Re: New Variable in CFX Post
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frank
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you can try the following:

1. cfx-post, click variable table, then right click > new>name. 2.select the method= expression >vector. 3. input you definations. 4.a user defined variable will appear under the variable table.
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Old   August 25, 2008, 11:16
Default Re: New Variable in CFX Post
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John S.
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Another method would be to create and expression in Post defined as Vorticity * Velocity and then simply create a variable that references that expression.

For example, when I run my CFD I usually create an expression for the reference pressure, Pref, which I subtract off from the value I set at pressure specified inlets/outlets. When I post process and want to calculate the absolute total pressure, I create an expression (usually called ptpsi or something) and define it simply as Total Pressure + Pref. I then create a new variable called PT abs and reference it to the expression ptpsi. That way when I want to do any calculations or contours involving total pressure I can specify my new PT abs variable and not have to do any manual pressure corrections.

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Old   August 26, 2008, 16:28
Default Re: New Variable in CFX Post
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CycLone
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Did you want Vorticity times Velocity or Vorticity dot Velocity? For the latter you need to write expressions for each component.

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Old   August 28, 2008, 22:47
Default Re: New Variable in CFX Post
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Ben
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Thanks for the reminder.. I am interested in vorticity 'cross' velocity. Does this mean that I will have to write the expression for each of the component in ANSYS? Or does ANSYS CFX instantly recognize in the expression function that: vector x vector = "cross product of vectors"?
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Old   August 29, 2008, 16:18
Default Re: New Variable in CFX Post
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CycLone
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Post doesn't currently do vector arithmetic, so you need to input the expressions. Which isn't really much work, we've already done more typing in this discussion alone!
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Old   September 1, 2008, 00:37
Default Re: New Variable in CFX Post
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Ben
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Ok, cheers for the input!
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Old   March 27, 2012, 09:35
Default Create expression in CFD-Post
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pritam gole
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I am trying to create a new expression in cfd-post for Nussult number i.e

Nu = h*d / k
But not succeded,i done with heat transfer coefficient i.e 'h' at perticular interface but not with 'Nu'

please help
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Old   March 27, 2012, 17:48
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Glenn Horrocks
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Have a look in the CFX tutorials, I know some of them define post-processing variables. That will show you how to do it.
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Old   June 20, 2012, 18:10
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soni
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Hi Ghorrocks,

How can we define variables in CFX post? You mentioned its in tutorials but I found defining variable in CFX pre. Is there a way to define in post?I have to plot the contour of pressure coefficient at the mid span of turbine blade.

I would really appreciate your help

Thanks
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