[moeinvh]

Hi friends,

I have the following problem with UDF for velocity inlet:

I have 64 holes as "inlet" which all of them have the same velocity profile. The velocity profile is in the form of 1-r^2 (if the origin was at the center of each hole).

I wrote the following UDF for x-component inlet velocity:



#include "udf.h"
DEFINE_PROFILE(inlet_x_velocity, thread, position)
{
real x[ND_ND]; /* this will hold the position vector */
real y, z, D;
face_t f;
D = 0.03; /* inlet diameter in m */
begin_f_loop(f,thread)
{
F_CENTROID(x, f, thread);
y = 2.*x[1]/D; /* non-dimensional y coordinate */
z = 2.*x[2]/D; /* non-dimensional z coordinate */
F_PROFILE(f, thread, position) = 10. *(1.0-y*y-z*z);
}
end_f_loop(f, thread)
}



The problem is that this profile works correctly only for the centroid hole because, in other holes, y and z components are not equal to zero at the center of the hole.

In other words, I need to define new origins at the center of all inlet holes.

Is there any idea to solve the problem and generalize the UDF for all inlets?

Thank you.

[LuckyTran]

To generalize it, you would need to calculate the centers on the fly based on the grid and not any user input. So you'd have to loop over the face cells, get all the x,y,z's and calculate the center.

[moeinvh]

Originally Posted by LuckyTran

To generalize it, you would need to calculate the centers on the fly based on the grid and not any user input. So you'd have to loop over the face cells, get all the x,y,z's and calculate the center.

Thank you for your answer,

But, would you please tell me what exactly I should do, step by step?
For instance, I don't know what does the "fly based" means and so on...

[moeinvh]

Originally Posted by LuckyTran

To generalize it, you would need to calculate the centers on the fly based on the grid and not any user input. So you'd have to loop over the face cells, get all the x,y,z's and calculate the center.

For instance, I guess one way is finding the maximum and minimum values of y and z components for each hole that the center of the hole is their average but, I don't have any idea about finding the max and min values of y and z components for each inlet hole.

After that, how can I set the found center point as a new origin?