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-   -   BC: inletOutlet,buoyantpressure,and \$interFields (https://www.cfd-online.com/Forums/openfoam-solving/109833-bc-inletoutlet-buoyantpressure-interfields.html)

 sharonyue November 27, 2012 21:49

BC: inletOutlet,buoyantpressure,and \$interFields

hi Foarmers:

I have been learning using OF for 3 months,now I am facing some tiny difficulties about BC.

I see in alpha1 dictionary, you can set
Code:

```OUTLET     {         type            inletOutlet;         inletValue      uniform 0;         value          uniform 0;     }```
I interpret it as air can get in and get out, but while simulating , I find it water can get out too, so what does this mean?

in p_rgh dictionary,
Code:

```walls     {         type            buoyantPressure;         value                uniform 0;     }```
I dont get this buoyantPressure , ,,,some other cases set:
Code:

```walls     {         type            fixedFluxPressure;         value          uniform 0;     }```
what does this fixedFlusPressure mean and the difference between buoyantpressure?

also in p_rgh dictionary

Code:

```outlet     {         type                fixedValue;         value          \$internalField;     }```
Does this \$internalField mean it is calculated by the internaFields? can I just modify it to
Code:

```atmosphere     {         type            totalPressure;         p0              uniform 0;         U              U;         phi            phi;         rho            rho;         psi            none;         gamma          1;         value          uniform 0;     }```

and the k and epsilon dictionary, I know k can be caculated by 1/2*(u^2)....,but some time it cant be set this way, so I dont know how to set the value of them.....

 sharonyue November 29, 2012 03:04

can anyone give me a hint?

 Ahmed Khattab December 27, 2012 07:41

Hi,

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

regards,

 jiujiumin July 18, 2013 06:51

hi you offer the site that look like not very helpful

Quote:
 Originally Posted by rebel ahmed (Post 399209) Hi, please check this thread, http://www.cfd-online.com/Forums/ope...onditions.html regards,
hi you offer the site that look like not very helpful, i want to know the diference between buoyantpressure and fixedfluxpressure.

 JR22 August 26, 2013 19:54

buoyantpressure vs fixedfluxpressure

I have a buoyantBoussinesqPimpleFoam that crashes if I use buoyantpressure , but converges perfectly if I use fixedfluxpressure. I've seen both BCs used in p_rgh. Anybody care to comment? Thanks

 sharonyue August 26, 2013 19:59

Sorry, I still dont know the difference between buoyantpressure and fixedfluxpressure.

 Sherlock_1812 May 28, 2014 08:02

Any clarity on the difference between them yet, sharonyue?

 sharonyue October 16, 2014 03:25

Quote:
 Originally Posted by Sherlock_1812 (Post 494494) Any clarity on the difference between them yet, sharonyue?
Hello!

Now I know that the difference between outletInlet and inletOutlet,

outletInlet:

outlet is a fixed value and inlet is zerogradient. Thats means if you set outlet value to be 0, so only 0alpha phase can get out. but any phase can get in.

inletOutlet:

vice versa.

Now I still dont know the difference between buoyantPressure and fixedFluxpressure. But looks like the first one is always used in VOF but the second one is used in two-fluid model. Im not sure.