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Old   November 10, 2016, 13:29
Default Solid temperature gradient
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urosgrivc
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Is it posible to make a variable in CFXpre for Temperature gradient within a solid domain?

Temperature gradient_(x,y,z) is what I would like to use vithin cfxpre.

is it posible to make an aditional variable for it?

Thank you

Last edited by urosgrivc; November 11, 2016 at 11:18.
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Old   November 10, 2016, 17:18
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Does Temperature.grad_x work?
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Old   November 11, 2016, 03:41
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Thank you mr. Glenn,

But the Temperature.grad_x does not work.

Let say I would like to monitor: volumeavg(Temperature.grad_x)@mydomain

It comes up with error:
The solver does not support the use of this operator for this variable when used as an argument for this function.

Althoe I can use this expression in cfxpost and the unit is [K m^-1] which is good.


Static enthalpy gradient would also be usefull to me, but ewerithing works until I include GRADIENT of that variable

This must be posible somehow as I am able to make two poits and do it manuali.

Last edited by urosgrivc; November 11, 2016 at 11:17.
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Old   November 11, 2016, 04:53
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How about using a few lines of CEL:

a=Temperature.grad_x
b=volumeAve(a)@mydomain

Sometimes splitting the function into components like this side-steps the restriction.
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Old   November 11, 2016, 05:00
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Thank you again

I have tried this and is still not working, it puts out:

...>has an invalid argument, 'a'. Only arguments that consist of a single recognised variable name are supported by the solver.
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Old   November 11, 2016, 05:04
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Can you attach your CCL?
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Old   November 11, 2016, 05:12
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this is the ccl file:
it is a very simple geometry, it is a cube with two oposing circle inprinted faces
one is at T=100C the other one is at T= 200C all other faces are adiabatic, material is modified steel.
I am sory I have exported all data so there is a lot of useles material data also included.

ccl= https://drive.google.com/file/d/0Bw9...ew?usp=sharing

geometry in cfxpost with temp grad contour (expresions deactivated, so the solver runs) https://drive.google.com/file/d/0Bw9...ew?usp=sharing

Last edited by urosgrivc; November 11, 2016 at 06:18.
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Old   November 11, 2016, 06:33
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I have found why this doesent work:

CFX reference Guide (page 229)
or
help->Quantitative CEL Functions in ANSYS CFX

In CFX-Pre the operand cannot be a CEL expression or any operand qualified by <Variable_Operator>.
However, you can create an Additional Variable based on any expression and then use the
Additional Variable as the operand. "How can I do this?"

The operand always uses the conservative values unless the
Boundcon variable operator is specified (for details, see Data Acquisition Routines in the CFX-Solver
Modeling Guide). For primitive or composite mesh regions, conservative values will be used even if
the Boundcon variable operator is specified.

<Variable_Operator> = grad = Gradient

Now I can see mr. Glenn why you proposed decomposition of expression and why it is still not functioning.
But I haven't figured it out yet
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Old   November 11, 2016, 11:58
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As mentioned in the documentation, operators nor expression are supported in the argument list of quantitative CEL functions such as volumeAve.

A common practice is to copy the gradient to an algebraic additional variable, say MyTempGrad

Steps:
- Create Unspecified Vector Additional Variable
- Activate Additional Variable in the Domain panel
- Fill in the additional variable components

xValue = Temperature.Gradient X
yValue = Temperature.Gradient Y
zValue = Temperature.Gradient Z

Create monitor point expressions using

volumeAve(MyTempGrad_x)@domain
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Old   November 11, 2016, 13:09
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Thank You very much Opaque and Glenn,

It is working now,
I am looking forward to implement this on my real model.
+It has opened new uses of cfx for me

Thank you for Your time.
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Old   November 14, 2016, 09:43
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Is it posible to change material properties based on a TRANS_LOOP comand.

I would like to set material thermal conductivitiy based on the heat flux results from previous timestep, I have basicly tryed this already but results arent vhat I was expecting.

The goal is to make some kind of topology optimization loop for thermal path optimization.

Like this: https://drive.google.com/file/d/0Bw9...ew?usp=sharing And loop this

To get best thermal conduction path from steady state https://drive.google.com/file/d/0Bw9...ew?usp=sharing to optimized to let say 50% mass

Last edited by urosgrivc; November 14, 2016 at 11:40.
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Old   November 14, 2016, 17:00
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This does not appear to be a simulation I would do in CFD. If I was doing this I would write a finite difference solver in python or matlab. You could also consider FREEFEM or some general PDE solvers as well.

Then you have complete control over everything. And you are just dealing with the heat equations so the equations you are modelling are straight forwards.
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