[firfilik]

we have unit cell, lenght of it 3.66 m and we want to define momentum source at certain intervals with udf. How would I define it.

[mprinkey]

You need to build DEFINE_SOURCEs for all three momentum components. The DEFINE_SOURCE will pass the cell and thread when it is called. You can use that to look up the cell centroid with C_CENTROID(X,cell,thread) where X is real X[ND_ND]. Then you can compute the momentum sources based on position information. It is a pretty textbook application of the DEFINE_SOURCE UDF mechanism.

[firfilik]

thank you Michael but I could not figure out how ı would place momentum source at 2 meters or 3 meters in udf

[mprinkey]

Originally Posted by firfilik

thank you Michael but I could not figure out how ı would place momentum source at 2 meters or 3 meters in udf

Come on! You have the location vector for each cell as the DEFINE_SOURCE is called using the C_CENTROID macro. So, put in some tests to check if the cell is located near where you want the source and if so, set the source to the value you need. Otherwise, set it to zero.

DEFINE_SOURCE is one of the easiest UDFs to code. All of the parts on in the basic example in the ANSYS documentation.

https://www.sharcnet.ca/Software/Flu...udf/node46.htm