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-   -   Pls answer my simple doubt concerning pathlines (http://www.cfd-online.com/Forums/fluent/50826-pls-answer-my-simple-doubt-concerning-pathlines.html)

Jig March 10, 2009 13:08

Pls answer my simple doubt concerning pathlines
 
I wanted to INCREASE the number of pathlines as in I want to make them more dense ..... i have gone through the Fluent User guide but have not found anything yet .....

I wanted to make them more dense so that i can clearly see the pathlines near the airfoil .... as of now just 2 pathlines are going near my airfoil :( .....

I cannot use velocity field because I wanted to animate using pathlines ..... pls help me/.

thanks in advance.

Novice March 11, 2009 09:15

Re: Pls answer my simple doubt concerning pathline
 
Hi,

I think you have to increase the number of steps in the pathlines definition panel.

Regards,

Novice

Jig March 11, 2009 12:20

Re: Pls answer my simple doubt concerning pathline
 
thanks but I have tried increasing steps it doesnt work :( ...... changing steps just increase/decreases the motion along x direction.

I could use velocity field as they are quite dense but I cannot animate using them ... Or can I ? does anyone know how to animate using velocity field?

Pls help me . i just want my first fluent simulation to be readY!

thanks.

sa March 11, 2009 14:03

Re: Pls answer my simple doubt concerning pathline
 
you have make the axial plane from where you can release pathlines

hervé March 12, 2009 05:10

Re: Pls answer my simple doubt concerning pathline
 
Are you trying to visualise the flow in a separation/recirculation zone? If yes, you 'll never get the pathline in this area, if you inject them from the upstream inlet. By definition, a separation zone is a "dead" zone, therefore no "fresh" fluid visits it.

To visualise a separation/recirculation zone, the pathlines should not be injected from the inlet, but from a vertical median plane, which should contain the airfoil and the separation zone. Indeed, the number of steps should be reduced (15 max, for instance), and because of the large number of cells concerned by the injection (it is a whole plane now, and no more just the inlet), I recommend to use the "path skip" function (says 5 for instance) to reduce computation and time of display.

Hope it helps.


Jason March 12, 2009 10:23

Re: Pls answer my simple doubt concerning pathline
 
Create a rake upstream of your airfoil. A pathline will be released from each point on the rake, so how ever many points you specify on the rake will determine how many pathlines you get.

Pathlines are released from each node on the surface you release the pathlines from. If you only get 2 pathlines that implies that either the pathlines can't be calculated (poor choice in surface to release from, or problem with overall setup) or you have an extremely coarse mesh.

Good luck Jason

Jig March 12, 2009 11:28

Re: Pls answer my simple doubt concerning pathline
 
thank you ..... I am trying to simulate steady incompressible flow through an airfoil...The plots are all fine .... I just wanted to make an mpeg file of the animation ... I am releasing the pathlines from the inlet surface..... The problem is that the pathlines are released at a distance of 1 cm from each other and I just wanted to reduce this distance .... my airfoil is imported from NACA0012 'dat' file... coordinated vary from 0 to 1 along x....

Jig March 12, 2009 11:42

Re: Pls answer my simple doubt concerning pathline
 
thank you ..... I am trying to simulate steady incompressible flow through an airfoil...The plots are all fine .... I just wanted to make an mpeg file of the animation ... I am releasing the pathlines from the inlet surface..... The problem is that the pathlines are released at a distance of 1 cm from each other and I just wanted to reduce this distance .... my airfoil is imported from NACA0012 'dat' file... coordinated vary from 0 to 1 along x....


Jason March 12, 2009 11:44

Re: Pls answer my simple doubt concerning pathline
 
Create a rake and release from there

Jig March 12, 2009 11:49

Re: Pls answer my simple doubt concerning pathline
 
thank you I will try that :) .....

DonTomasso March 16, 2009 17:07

Hi!
I have had the same problem. What I did was an adaptive refinement of the grid az the inlet, thus you get more cells -> more streamlines released -> denser streamlines!
But maybe the rake thing is easier..Jason, please, what is a rake, and how do you create one?
Cheers, Tamás

Micael March 16, 2009 19:55

Surface -> Line/Rake

For "Type" choose rake

Then define the two end points of the rake and the number of point to distribute on that rake.

Have a nice day.

Micael

Micael March 16, 2009 19:59

DonTomasso,

Directly taken from the user guide (27.5 Line and Rake Surfaces):

"A rake consists of a specified number of points equally spaced between two specified endpoints."

Have a nice day.

Micael

DonTomasso March 17, 2009 02:14

Thank you, have a nice day, too!


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