Convergence issue with Unsteady particle tracking with unsteady flow.
 

Hello there,

I am working on the spray modelling with the fluent. Using DPM model for unsteady particle tracking of diesel-liquid with the unsteady continuous fluid as air. Before the injection starts, I am getting convergence at around 250 iteration per time step, but as spray starts, the number of iteration per time step increases and after few time steps it doesnt converges even at 5000 iteration per time steps. I am running short of time and I dont understand the problem. Please let me know if you have some idea.
I am also confused with the courant number I am using. I have pressure based solver ( because fluent doesnt allows the density based solver with the PDF approach in non-premixed module). I am using courant number as 10. I am still confused that, what is the significance of Courant number with my pressure based solver ? Time step size I am using is 1e-5.

Please please let me know, if you have any idea about the problem mentioned. Any help is highly appreciated.
Thanks a lot !!!