[sharonyue]

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

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,

walls
    {
        type            buoyantPressure;
	value		uniform 0;
    }

I dont get this buoyantPressure , ,,,some other cases set:

walls
    {
        type            fixedFluxPressure;
        value           uniform 0;
    }

what does this fixedFlusPressure mean and the difference between buoyantpressure?



also in p_rgh dictionary

outlet
    {
	type		fixedValue;
	value           $internalField;
    }

Does this $internalField mean it is calculated by the internaFields? can I just modify it to

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.....

your help is very appreciated.Thank you in advance.

[sharonyue]

can anyone give me a hint?

[Ahmed Khattab]

Hi,

please check this thread,

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

regards,

[jiujiumin]

Originally Posted by rebel ahmed

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]

Anyone knows the answer to the question in this thread?

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]

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

[Sherlock_1812]

Any clarity on the difference between them yet, sharonyue?

[sharonyue]

Originally Posted by Sherlock_1812

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.

Any comments is welcomed.

[wyldckat]

Quick answer - Have a look at this thread: http://www.cfd-online.com/Forums/ope...xpressure.html