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

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.

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.

Did you want Vorticity times Velocity or Vorticity dot Velocity? For the latter you need to write expressions for each component.

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"?

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!

Ok, cheers for the input!

[pritam1688]

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

[ghorrocks]

Have a look in the CFX tutorials, I know some of them define post-processing variables. That will show you how to do it.

[soni_sth]

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