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Interpolate time averaged values

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Old   October 8, 2015, 12:32
Question Interpolate time averaged values
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Rikard
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Hi!
I wonder if someone can help me, i've searched in this forum an Ansys user guide but can find a solution.

I have a problem where the flow field is hard to converge in a steady simulation but works fine when I do it transient. I then want to calculate the dispersion of a passive scalar in the field and to save computational power I want to use the "frozen" steady flow field.

Is it possible to use the time averaged field from the transient simulation to solve the transport equation.

I can save the time averaged values for post processing but how to read it into fluent?
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Old   October 12, 2015, 00:14
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Lucky
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You can freeze the velocity field by disabling the flow and any other equations you don't need.

In the GUI go to solution controls => equations and uncheck flow,etc.

This will freeze the velocity field at the current time-step (it will not use the time-averaged velocity field).

What you need to do is patch the instantaneous velocity field with the mean field. The mean field is stored as a separate variable. Unfortunately Fluent won't let you reference a builtin variable so you must create a custom field function.

Create a custom field function for each of the mean quantities:
custom-function-0 = mean_x_velocity
do this for all quantities (mean_y_velocity, mean_temperature, etc).

Then you can patch the instantaneous x-velocity, y-velocity, z-velocity to the custom function. Just make sure you patch everything and don't forget any important variables.
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