Annexe : utilisation of fluent


 
 

1) Custom Field Functions

2) Adapting the grid

2.1) Define new zones
2.2) Refine the grid
3) Patch a function to a zone

4) About Macros
 
 



 
 

1) Custom Field Functions
 

It is often interesting to define new functions adapted to our problem.
For example, if you want to initialise the velocity vectors or the temperature, the Custom Field Functions are very usefull.

Follow the instructions.
 

follow the rolling menu
 

Write the functions you need with all the variables you dispose in Fields Functions.
Then give a name to your function
 


 

Click on Define.
There is an illustration of the use of the Custom Field Functions in the 3) Patching a function.
 

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2) Adapting the Grid
 

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2.1) Define new zones

In our simulations, we needed to impose different initial conditions of temperature in several areas.
So, we had to separate the grid. This method is allowing the definition of new zones without going back to the Prebfc program.

  View of the grid before the adaptation.
 

initial grid
 
 

Follow the instructions.
 

follow the rolling menu Adapt Region
 
 

Then, you must define the zone you want to separate from the grid.
Write the two coordinates (in meters) that define the rectangle area.
 


 

Then, click on Mark.
Now, you have to separate the cells you choose from the grid. For that, follow the instruction.
 

follow the rolling menuGrid Separate Cells
 
 

Select the hexahedron you just define in "Region Adatation" and the zone you want to separate from it.
 


 

Then click on Separate.
Note: You must Adapt and Separate the zones one after one. To adapt all the zones then to separate them doesn't work.
 

View of a part of the grid after the adaptation. We are able now to give different boundary conditions or initial conditions in each zone.

view of a part of the grid
 

Example: There are different initial conditions of temperature in three zones after the patching of custom field functions.


 

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2.2)  Refine the grid
 

This is an explaination of the refinenment of the grid with an example. We will adapt the grid based on the temperature gradients in the solution of two rolls.
Before adapting the grid, you will first determine an acceptable range of temperature gradients over which to adapt

When your solution is converged, follow the instructions.
Choose the good options for the Contours.
 

Display Contours
 

Note: Examining the cell-by-vell values is helpful when you are preparing to do an adaptation of the grid because it indicates the region where the adaptation will take place.
 

View of the temperature in each cell
 
 

Then, go back to Display Contours and select Adaptation and Adaption Function in the Contours Of drop-down list.
 
 

select the good "Contours Of"
 

Click on Display.
 

View of the temperature gradient
 

Go back to Contours and deselect Auto Range so that you can change the minimum temperature gradient value to be plotted.
Enter a new value of 2e-06.
Click on Display.
 

Be careful with the Options
 

Contours of the gradient over a limited range
 

Then follow the rolling menu.
 
 

follow the rolling menu
 

Select Temperature and statistic temperature in the Gradients Of drop-down lists.
Deselect Coarsen under Options, so thatonly a refinement of the grid will be performed.
Click on Compute.
Now enter the value of 2e-06 for the Refine Threshold.
 

Be careful to the instructions
 

Then, click on Mark.
Click on Manage
 


 

Click on Display then on Adapt.
 

cells marked for adaptation
 

View of the grid adapted.
 


 

Then, you can iterate again and obtain a better solution.
 

The new solution converged
 
 

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3) Patch a function to a zone
 

For the initial condition, it is very interesting to patch functions to differents zones.
 

follow the rolling menu
 

Then select  the Variable, the Field Function and the Zones To Patch.
 

select what you want to patch
 

It is very interesting to define new zones so that you are able to patch different functions to different zones.
For example: The initial condition on temperature following.
 


 
 

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4) About Macros
 

The Macros allow to see the evolution of different fields during the convergence.
Select Solve Monitor Command.
 

follow the instructions
 

Click on Define Macro...
Then for example, define the macro following: Display Contours Temperature, click on Display.
Then, click on End Macro on the Monitor Commands.
Activate the macro and give it the same Command name than the name of the macro

To save a macro, write file then click return, then write  write-macro.
 

to save a macro
 
 

If you want to load a macro, follow the rolling menu.
 


 

After the reading of the macro, look at the Monitor Command if the name of the Command is the good one.
 


 

Click on Define Macro to see if your macro is already imported.
 


 

Note: If you want to have your macro display on an other window than the residual, follow these instructions.
 


 

You can now activate several windows.
 


 

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