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-   -   CEL Function for moment acting on a BC? (http://www.cfd-online.com/Forums/cfx/20773-cel-function-moment-acting-bc.html)

NymphadoraTonks November 3, 2004 10:58

CEL Function for moment acting on a BC?
 
I notice that there are several built in functions for outputing the net X,Y and Z flow induced forces acting on a BC.

Is there a way to output the net moments due to flow induced forces acting on a body?

There dont seem to be built in functions for this?

The BC I'm fiddling with describes an anisotropic-shaped hollow cutout in the fluid domain and as such is not amenable to simple point-of-action assumptions.

TIA

Glenn Horrocks November 3, 2004 17:18

Re: CEL Function for moment acting on a BC?
 
Hi,

You could make an additional variable of the cross product of the elemental force and the axis you are taking your torques about. Then you can integrate them over the surface and get the total torque.

Glenn Horrocks

NymphadoraTonks November 4, 2004 02:29

Re: CEL Function for moment acting on a BC?
 
That's what I thought ...

So no built in function but I can do this in user fortran? You wouldn't be able to do this in a user CEL function I take it?


Juan Carlos November 4, 2004 11:57

Re: CEL Function for moment acting on a BC?
 
Take a look at the etc/VARIABLES file in the installation directory. There is a callback named torque that seems to work as the force callback.. It may compute the torque respect the position vector on the global frame.

Juan Carlos

Robin November 10, 2004 18:01

Re: CEL Function for moment acting on a BC?
 
The torque is given about a global axis. If you need it about another axis, it is a trivial calculation to do. You simply need to take the torque about each axis and the forces in each direction, then apply simple statics to do the transformation. All of the above are available as CEL integration functions.

Regards, Robin


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