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-   -   Structure of the Phi File (http://www.cfd-online.com/Forums/phoenics/51218-structure-phi-file.html)

 Mark Russell July 2, 2001 11:49

Structure of the Phi File

I am writing a routine to get at the results from the Phi file. That way I can perform some simple analysis on the numeric results.

My question, for 2d cases, in the res' file, which is data extracted from the Phi file, there is no data shown for the U1 component at the IX = IXMax location. Similarly there is no V1 data at the IY = IY Max location. Why?

If this is a function of the staggered grid, then I suspect these velocity values are those which arise at the entry to the cell and not at the cell centres. Is that correct?

What then is the data that is displayed by the Virtual Viewer? Is that simply interpolated 'grid line' data for the 'cell centres'?

Any notes, or pointers to relevant Cham help pages, gratefully received

 Kike July 3, 2001 04:38

Re: Structure of the Phi File

Dear Mark

The value for U1 at east faces of cell IX=IXL corresponds to the boundary condition you have for your domain at EAST boundary. The same is valid for V1 component at NORTH boundary.

If you draw the control volume for say the U1 velocity at the last cell (IX=IXL), you will see there is no way to contruct an equation for it. This velocity is associated to the outgoing momentum flux and it is controled by your BC, or the pressure value at IX=IXL.

PHOENICS do not solve the velocity for this node except if XCYCLE=T. I have assumed you are not using CCM method to solve the velocities.

By default, the values for velocity components into the PHI(PHIDA) file correspond to those cell faces, ie. east and north in 2D. You can obtain cell centered velocity representation in PHOTON and it is achieve by interpolation. I am not sure, but I think it is the principle that VRViewer employs.

Regards

Kike

 Dora Xenidou October 5, 2001 05:27

Re: Structure of the Phi File

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