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-   -   Modified boundaries for InterFoam (https://www.cfd-online.com/Forums/openfoam-solving/59500-modified-boundaries-interfoam.html)

 kumar2 February 22, 2006 01:32

Hello friends I am using th

Hello friends

I am using the InterFoam solver to look at flow over a bump. this is a popular example from hydraulics. But i have to modify all the boundaries. For example at the inlet , the gamma is 1 below the free surface and 0 above it. similarly at the outlet the pressure is 0 above the free surface and varies linearly below it.

although both the inlet and outlet are fixedValue types how can we give a variable say gamma or pressure changing across the boundary.
ideally this should be through a small subroutine ( that is how this was implemented in Comet) . In all the tutorials the fixedValue are uniform . But how can we give a function there ??

kumar

 kumar2 February 23, 2006 23:31

Can anybody please give some i

Can anybody please give some inputs for this problem

thanks

kumar

 jens_klostermann February 24, 2006 03:28

Hi kumar, This question has

Hi kumar,

This question has been asked many times, just search for nonuniform in the forum.

I did for example like in http://www.cfd-online.com/OpenFOAM_D...es/1/1118.html

Regards
Jens

 michele February 24, 2006 04:48

Kumar, I would suggest to spe

Kumar,
I would suggest to specify two inlet patches directly inside the mesh: the first with gamma = 0 and the second with gamma = 1.

Be careful that in the interFoam solver the pressure variable is the "modified pressure pd". An hydrostatic distribution is represented by a constant "pd".
Regards,
Michele.

 kumar2 March 2, 2006 05:30

Hi Michele 1. Thanks a lo

Hi Michele

1.
Thanks a lot for your e-mail. But i am really confused with the modified pressure . for example in the interFoam tutorial on breaking dams , when i looked for boundary values for pd in /damBreak/0/pd file . i was surprised to find that p0 is specified. First question is how is pressure modified (pd) calculated from p0

2. If for example there is a channel about 0.3 m deep with water level say at 0.15m , and water velocity is 0.8 m/s . Then the total pressure would be the hydrostatic pressure(rho*g*h) + hydrodymanic pressure(1/2 *rho*V^2 ). The units of the total pressure would be KG /M/S^2 . If as you say the hydrostatic pressure is constant then isn't there a division by 'h' . but in that case the units would be different from [1 -1 -2 0 0 0]. Could you please tell me the p0 and p modified at the free surface and bottom of the channel.

 paka August 16, 2007 03:27

Can anyone provide some more i

Can anyone provide some more input about "modified pressure"?

I'm using rasInterFoam solver with dam break problem. Looking at present results, I assume the same "modified pressure" exists in my case.

When I view the pressure at one of initial times (i.e. 0.04s) the pressure is constant along whole height, which one would expect to be hydrostatic and it isn't.

Can anyone provide some input, how to obtain the total REAL pressure values during whole run?

Kumar? How did you deal with that?

Thanks and best regards,
Krystian

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