Hello I recently talked about my theory for propeller rpm and thrust with airflow in this post
I was wondering how I would calculate the propeller rpm at a certain speed if there was no power applied to the propeller so I can find the actual thrust of the propeller at a certain speed by adding the rpm it would be at a certain speed with no power and the extra rpm the propeller adds?
What I would try here, is to compute the flow speed that the propeller produces at a certain rpm, without the external flow. This should help you get close to the operating point, and then you can add the external flow speed.
For this, setup your simulation with a pressure inlet/pressure outlet boundary condition combo, apply the desired rpm and measure the average flow speed produced solely by the propeller rotation.