I would like to simulate a closed-loop system on ANSYS. Ultimately, my goal is to simulate the whole cardiovascular system with the main arteries and veins. For now, I'm just using a circular pipe with an open section to separate the inlet from the outlet, my question is: is it possible to re-inject a particle each time it escapes through the outlet into the inlet? I was thinking on using UDFs for the nanoparticles re-injection, but I have no clue where should I use the UDF once I define it or is there a easier way to do this without using UDFs? I was also looking at the documentation here for defining UDF for DPM, but I don't know which one to use (maybe a combination of some of them?). Any guidance for this would be appreciated. I also attached a zip file containing the workbench, geometry and mesh file for the sample model I'm using. If you need any other info to help me please let me know.