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-   -   movingRotatingWallVelocity (http://www.cfd-online.com/Forums/openfoam/67310-movingrotatingwallvelocity.html)

ternik August 11, 2009 13:36

movingRotatingWallVelocity
 
Hi all,

within OF1.5-dev I am trying to use "movingRotatingWallVelocity" (for Taylor-Couette problem). Here is my set for this type of boundary conditions (for velocity):
.
.
.
WallRotating
{
type movingRotatingWallVelocity;
centre (0 0 0);
axis (0 0 1);
rpm 10;
value uniform (0 0 0);
}
.
.
.

Unfortunately I can not find any reasonable (physical) description for "value"; can anybody , please, explain what is "value"!

Thanks in advance.

ebertmp August 11, 2009 14:23

I don't have the code in front of me, but I'm pretty sure it is not being used. So you should be able to set it to anything and be ok. Also, beware in earlier revisions of 1.5-dev this BC was missing a 2*pi for converting rpm to rad/sec.

ternik August 12, 2009 03:36

Quote:

Originally Posted by ebertmp (Post 225983)
I don't have the code in front of me, but I'm pretty sure it is not being used. So you should be able to set it to anything and be ok. Also, beware in earlier revisions of 1.5-dev this BC was missing a 2*pi for converting rpm to rad/sec.

Thanks for the answer! Examining the movingRotatingWallVelocityFvPatchVectorField.C file looks like the "value" (by the way it should be set as a vector!) is not used in calculation of rotational speed but it is used for the following:


void Foam::movingRotatingWallVelocityFvPatchVectorField ::write
(
Ostream& os
) const
{
fvPatchVectorField::write(os);
os.writeKeyword("centre") << centre_ << token::END_STATEMENT << nl;
os.writeKeyword("axis") << axis_ << token::END_STATEMENT << endl;
os.writeKeyword("rpm") << rpm_ << token::END_STATEMENT << endl;
writeEntry("value", os);
}

Last but not least, the rotational speed is calculated (I think properly) as:

vectorField Urot =
(axis_ ^ (patch().Cf() - centre_))*rpm_*2*mathematicalConstant::Pi/60;

Cheers,
Primoz.


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