Effective Strategy for ensuring convergence using FLuent's Fan Model
If we switch on the fan model at the start so that it computes the Pressure Jump
from a fan curve, it is found that the solution diverges after sometime and it predicts unreasonable mass flowrates. Even limiting the max and min velocity range does not work. The solution is not to switch on the fan model at the start.  Run the case for some iterations to get reasonable convergence.  Determine the guess mass flow rate from the fan plane.  Calculate the pressure rise for this guessed flow rate from the fan curve.  Input this constant pressure rise in the PressureJump option in fan model.  Run the case with this constant pressure rise for some iterations till we get reasonable mass flow rates (within limits).  Now switch on the the Polynomial option of Fan model to calculate the pressure rise from fan curve.  Run it till we get the reasonable convergence. 

