[xab]

Is there any way to know the components of normal vector in a boundary wall in order to use it in a custom field function?

Thank you in advance
Xabi

[`e`]

Yes, use the f_normal[i] variable. Have a read of the example on reflecting particles from a boundary in the UDF Manual for usage.

[xab]

Thanks for your reply,

I'll try this way.
I don't have any experience working with UDFs so maybe has no sense what I am saying but I need to define the function I want to calculate with this UDF before calculating the solution or this UDF is just to allow me using the f_normal[i] variable?

Here is my case if it clears up a little bit:

I am simulating leakage through the tips of a gear pump but I am simulating just one tooth. I have imposed periodic conditions to the inlet and outlet so when calculating the solution the static pressure that gives fluent is without the pressure gradient and I need to create a custom field function to obtain the real pressure.
What I want to calculate is the pressure and viscous forces but related to the real pressure (fluent gives the forces related to the static pressure) so I need to integrate my variable and here is where I need the normal vector. My question is, do I need to define this integral in the UDF or just need this UDF to acces the normal vector? Is there any other way to calculate this force more easyly?

Thanks a lot
Xabi