Torque of Savonius turbine is not convergent

fsifsi · September 4, 2012, 22:16

Dear all,
I used Fluent 13 to simulate the Savonius turbine with obstacles was placed front of it as attached picture. k-w sst turbulence model and the second order discretisation were selected. However, I could not get convergence with time for Torque of turbine (Cm) while Cm is well convergent with time for the case of without obstacles.
Could you give me some advice, please.
Thanks.

husker · September 5, 2012, 04:04

Hi,

Flow is unsteady, so Cm is supposed to be unsteady. You have to consider other scalars to judge convergence. Then you will have an idea about how Cm oscillates.

Regards,

fsifsi · September 6, 2012, 01:29

Thanks,
Yes, the flow is unsteady so Cm should be oscillated, however, it should be repeated over one cycle or periodic of time.

Andrea1984 · December 6, 2012, 07:22

Hi fsifsi,

can I ask you how do you evaluate the turbine torque? Do you use the Cm value or the Momentum obtained from Result Reports?

Thanks,

Andrea

fsifsi · June 23, 2013, 21:52

I used Cm value

Far · June 24, 2013, 09:50

Lower the time step. how did you calculate the time step?

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September 5, 2012, 04:04		#2
husker Member Join Date: Mar 2009 Posts: 85 Rep Power: 17	Hi, Flow is unsteady, so Cm is supposed to be unsteady. You have to consider other scalars to judge convergence. Then you will have an idea about how Cm oscillates. Regards,

September 6, 2012, 01:29		#3
fsifsi Member le Join Date: Nov 2009 Location: seoul Posts: 34 Rep Power: 17	Thanks, Yes, the flow is unsteady so Cm should be oscillated, however, it should be repeated over one cycle or periodic of time.

December 6, 2012, 07:22		#4
Andrea1984 Senior Member Andrea Join Date: Feb 2012 Location: Leeds, UK Posts: 179 Rep Power: 16	Hi fsifsi, can I ask you how do you evaluate the turbine torque? Do you use the Cm value or the Momentum obtained from Result Reports? Thanks, Andrea

June 23, 2013, 21:52		#5
fsifsi Member le Join Date: Nov 2009 Location: seoul Posts: 34 Rep Power: 17	I used Cm value

June 24, 2013, 09:50		#6
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Lower the time step. how did you calculate the time step?