I have been working in a buoyant flow with solar radiation. The case without MRF gives results as expected and according the physics; however, when I include MRF to simulate a turbine, I got several errors like negative torque and reverse flow in the whole domain. The summary of what I have done is the following:
1) Simulating the case without MRF to get the airflow to design the turbine. The mass flow rate is 950 kg/s, and the upwind velocity 11 m/s for a diameter of 10 m (vertical component of the geometry). The following slice shows the velocity contours.
2) Designing a turbine with the previous mass flow rate and considering 15 rpm.
3) I keep the same BCs. The only difference with the previous simulation is the interfaces at the inlet and outlet of the rotor section. The turbine is placed in the bottom center of the domain. I assign a rotational velocity in that zone and then run the simulation.
The results are not even close as expected with that kinetic energy. At 5-10 rpm, I got reverse flow (it should be at higher), and at very low 0.1 rpm, negative torque.
So, in my understanding if the problem without MRF is running ok, and then I am applying normal conditions to simulate rotating flow, where could be the problem?
I have checked carefully the configuration and everything seems ok.