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Momentum by force equation in UDF

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Old   October 18, 2013, 06:14
Default Momentum by force equation in UDF
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I am simulating a wall by momentum equations in Cell Zone Conditions. The flow is stationary.
I have the force given by equation like:
F - force vector
c - constant
u - velocity vector
n - wall normal vector
Force generally is F=momentum/time derivative.
So, my question is, how to provide time in UDF in steady/stationary flow?

For example for X direction of flow I would have something like:
and I have to convert the force into momentum, so I would need to derive by time:

#include "udf.h"

real c, x_vel, L, source, n;


return source;

My question is how to write line:
in a proper way?

Thank you for help!
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