Impeller simulation

deep_cfd · May 10, 2016, 09:31

Hi everyone
I am trying to do analysis of an impeller.
I set total pressure inlet at 101325 pa and outlet static pressure of 330101
Rotation speed of 38k rpm
When i run the simulation with the viscous work term switched OFF everything goes well and i get my required mass flow pressure ratio and the flow is good in the passage without seperations and backflows
But when the simulation is run with viscous work term switched ON the flow get heavily disrupted above around 50pc span of the blade and my mass flow is heavily impacted
Without that option turned on i get more than 5 kg/s now after Switching it ON i get less than 0.5 kg/s PLZ HELP
do i need to keep it ON?

ghorrocks · May 10, 2016, 20:57

Does significant viscous heating occur? If no significant heating occurs then switch it off. Only use the option if you need it.

Why does viscous heating cause a difference? Assuming viscous heating is not significant; I suspect it has gone numerically unstable and/or has not fully converged. So the difference is just numerical error.

deep_cfd · May 11, 2016, 09:26

Thank G horrocks
I altered setup and got it working with viscous terms ON somehow fell into place.
The changes were to the inlet which was set as a rotating frame which was switched to a stationary frame.

May 10, 2016, 09:31	Impeller simulation	#1
deep_cfd New Member Join Date: May 2016 Posts: 3 Rep Power: 9	Hi everyone I am trying to do analysis of an impeller. I set total pressure inlet at 101325 pa and outlet static pressure of 330101 Rotation speed of 38k rpm When i run the simulation with the viscous work term switched OFF everything goes well and i get my required mass flow pressure ratio and the flow is good in the passage without seperations and backflows But when the simulation is run with viscous work term switched ON the flow get heavily disrupted above around 50pc span of the blade and my mass flow is heavily impacted Without that option turned on i get more than 5 kg/s now after Switching it ON i get less than 0.5 kg/s PLZ HELP do i need to keep it ON?

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May 10, 2016, 20:57		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Does significant viscous heating occur? If no significant heating occurs then switch it off. Only use the option if you need it. Why does viscous heating cause a difference? Assuming viscous heating is not significant; I suspect it has gone numerically unstable and/or has not fully converged. So the difference is just numerical error.

May 11, 2016, 09:26		#3
deep_cfd New Member Join Date: May 2016 Posts: 3 Rep Power: 9	Thank G horrocks I altered setup and got it working with viscous terms ON somehow fell into place. The changes were to the inlet which was set as a rotating frame which was switched to a stationary frame.