Naresh Patre
Ansys Employee

Hello soneill

Thanks for sending the file. I reviewed it and below are my observations:

1. The mesh seems to be too coarse as seen in the image below. I noticed that you have set the Solution Fidelity option to an extreme low. This will give you a very coarse mesh and reduce the accuracy of results. Please increase the mesh resolution so that you have reasonable mesh in the geometry. 


2. There are some steps in the geometry near the converging - diverging section of the pipe. Are the steps important in your simulation? If yes, then you need to have refined mesh to capture all the geometry details. If not, please clean up these geometry steps.


3. In your problem description, you mentioned that Mass flow at inlet is 40 kg/s. However, in the simulation you have specified mass flow as 135 kg/s. So please review your boundary conditions.

4. For units of Cv, please refer to this discussion thread.