# transonic rotor convergence problem

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 January 5, 2008, 06:30 transonic rotor convergence problem #1 Noureddine Guest   Posts: n/a Hi all, I faced same convergence problem as posted before by Samad in this forum, with an indication that the maximum Mach number increase too much. I have used CFX-TurboGrid 11.0 for mesh generation and the Turbomachinery template for the CFX-PRE 11.00 I want to know if somebody have successful to get a convergence with a transonic compressor (rotor37 i my case)? and if yes, plz, tell how you did it ? any other advice is welcome Regards Noureddine

 January 6, 2008, 06:59 Re: transonic rotor convergence problem #2 Noureddine Guest   Posts: n/a even I try to simulate the off-design flow (60% of design speed = 1080 rad/s) to have a subsonic axial compressor, I found same difficulty to converge. I used P-Total Inlet Mass Flow Outlet as boundary conditions, with, Reference Pressure = 1 atm, P-total = 0 atm, Mass Flow rate per Machine = 13.9 kg/s. what is the problem ? any help is very welcome. Regards Noureddine

 January 6, 2008, 12:20 Re: transonic rotor convergence problem #3 Noureddine Guest   Posts: n/a It's OK, i found my mistake, it was the direction of rotation !!!!, we should indicate the sign of the rotation as -1800 rad/s for the design speed.

 January 6, 2008, 18:23 Re: transonic rotor convergence problem #4 Amir Guest   Posts: n/a Hi Noureddine, Well i know you solved your problem but i have a small question. I am simulating a rotor in a stator (journal bearing) using turbomachinery template in CFX 11. I have a lubricant between my rotor and stator...When i do a transient simulation the residuals oscillating. did you have the same problem how did you solve it?

 January 7, 2008, 02:42 Re: transonic rotor convergence problem #5 Noureddine Guest   Posts: n/a Hi Amir, yes i had an oscillation of residuals in the last steps, but results was acceptable. sorry, i have solved only the steady flow of a transonic compressor and i did not deal with the transient rotor/stator simulation. Good luck Noureddine

 January 8, 2008, 08:46 Re: transonic rotor convergence problem #6 pankaj Guest   Posts: n/a Hi Noureddine! the negative sign is for your rotors rpm,which is not always common,it specifies the direction of rotation.

 January 8, 2008, 09:23 Re: transonic rotor convergence problem #7 Noureddine Guest   Posts: n/a Hi Pankaj, i know that's not always common, i am talking only about my own problem (own geometry) which is the axial compressor "rotor37". you are right, it specifies the direction of rotation. thanks for you message. Regards. Noureddine

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