[gejiabin]

There is an outflow boundary condition in fluent,then how to set the outflow boundary condition in openfoam?
The basic boundary condition is fixedValue,fixGradient,zeroGradient ,calulated..,other BCs derive from them,but I don't know which one is same as outflow boundary condition in fluent

[Ruli]

For simple outflow try

zeroGradient.

For further information check

tutorials/incompressible/simpleFoam/motorBike/0.org

Best regards
Julian

[mturcios777]

zeroGradient it a good suggestion. Since OpenFOAM is less "black box", it helps if you have a working knowledge of the theory of numerical simulation. Check the Wikipedia article for a decent overview:

http://en.wikipedia.org/wiki/Boundary_conditions_in_CFD

[gejiabin]

Originally Posted by Ruli

For simple outflow try

zeroGradient.

For further information check

tutorials/incompressible/simpleFoam/motorBike/0.org

Best regards
Julian

Hi,
in tutorials/incompressible/simpleFoam/motorBike/0.org,
https://github.com/martinep/foam-ext.../motorBike/0/U
U:
outlet
{
type inletOutlet;
inletValue uniform (0 0 0);
value $internalField;
}
https://github.com/martinep/foam-ext.../motorBike/0/p
p:
outlet
{
type fixedValue;
value $internalField;
}
inletOutlet may mean zeroGradient if fluid flows out,fixedvalue if fluid flows in, but I do not understand "value $internalField"?

[Ruli]

Originally Posted by gejiabin

inletOutlet may mean zeroGradient if fluid flows out,fixedvalue if fluid flows in, but I do not understand "value $internalField"?

$internalField is the initial condition defined in the top of the file. The first iteration uses this value for starting.

Best regards
Julian