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-   -   calculating mean streamwise velocity in LES (http://www.cfd-online.com/Forums/openfoam/79050-calculating-mean-streamwise-velocity-les.html)

maysmech August 10, 2010 18:16

calculating mean streamwise velocity in LES
 
Dear Foamers
i run a backward facing step case with pisoFoam LES.

Now, i want plot mean stream wise velocity diagram over a specific line.
i have values of stream wise velocity in all time steps but i don't know how can i reach a diagram which show mean stream wise velocity in last time steps. :confused: . please tell me its scheme in paraView or Tecplot.
(i know LES doesn't lead to steady state and doesn't have periodic manner but i saw different works which displayed mean stream wise velocity of BFS with LES.)

Best,

Simon Lapointe August 10, 2010 20:13

To obtain mean velocity (or other variables), you can use the fieldAverage function object during your simulation. This will calculate the average at each time step, and create mean fields.

For example, to average U and p just add the following to your controlDict :

functions
(
fieldAverage1
{
// Type of functionObject
type fieldAverage;

// Where to load it from (if not already in solver)
functionObjectLibs ("libfieldAverage.so");

// Fields to be averaged - runTime modifiable
fields
(
U
{
mean on;
prime2Mean on;
base time;
}
p
{
mean on;
prime2Mean on;
base time;
}
);
}
);

maysmech August 11, 2010 04:31

Thanks Simon,
I don't want mean velocity in each time step. i want mean velocity in several time steps in end of simulation times to display a diagram of mean velocity over a line. i don't know how many time step should be considered to show MEAN manner and how to calculate this value.
Best,

maysmech August 12, 2010 16:07

Any idea ?

Edison_Ge September 6, 2010 11:38

Quote:

Originally Posted by maysmech (Post 271339)
Any idea ?

I'm having the same problem. And I think the time average in the last time step is the result you are looking for. Just follow the link below and see how things go.

http://www.cfd-online.com/Forums/ope...tatistics.html


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