Could I activate the DPM_DRAG and DPM_BODY_FORCE at the same time? I can activate only one of them on the same panel, could i write the two codes into one file.c and compile it?

Thanks a lot!

Of course you can use these two together, but at one time you can only compile one udf file. Just put all of your udfs in a single file.

Yes, I put two files into the same file, what I want to do is activate the body force and the drag force at the same time (coupled with bulk gas iteration). could you give me some suggestion?

Thanks!

Yes, you can define "user defined function->body force" for the body force and specify "drag law" for your drag law, individually. I think you didn't click the pull-down of "drag law" of "drag parameters".