Rotating Frame Stationary Vaneless Diffuser?

khoopes · July 23, 2014, 13:22

I have a centrifugal impeller with a vaneless diffuser. It is simple in turbogrid to create a mesh that encompasses both impeller and diffuser with separate hub and shroud surfaces for the impeller and diffuser sections. My question is since it is one mesh, I have to solve the entire domain in the same reference frame. Is it possible or advisable to solve the entire domain in the rotating frame and set the diffuser hub and shroud surfaces as counter-rotating walls? This is not just an abstract question as I have already done many of these simulations like this and am now questioning the method.

Thanks,

Kevin

ghorrocks · July 23, 2014, 19:02

Yes, this is an acceptable method. In fact I would even say that if it is appropriate I would say it is the recommended method as it means you do not need a GGI in a critical part of the flow.

To be sure you should do a simulation with and without the frame change and check they are equivalent.

khoopes · July 24, 2014, 11:20

Thank you for your reply. Since I posted this yesterday I did a simulation with a split rotor and diffuser for comparison and the results look very similar. The metric that I am concerned with in this simulation was withing 0.5% which is fine for my application.

July 23, 2014, 13:22	Rotating Frame Stationary Vaneless Diffuser?	#1
khoopes Member Kevin Hoopes Join Date: Oct 2010 Posts: 43 Rep Power: 17	I have a centrifugal impeller with a vaneless diffuser. It is simple in turbogrid to create a mesh that encompasses both impeller and diffuser with separate hub and shroud surfaces for the impeller and diffuser sections. My question is since it is one mesh, I have to solve the entire domain in the same reference frame. Is it possible or advisable to solve the entire domain in the rotating frame and set the diffuser hub and shroud surfaces as counter-rotating walls? This is not just an abstract question as I have already done many of these simulations like this and am now questioning the method. Thanks, Kevin

July 23, 2014, 19:02		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Yes, this is an acceptable method. In fact I would even say that if it is appropriate I would say it is the recommended method as it means you do not need a GGI in a critical part of the flow. To be sure you should do a simulation with and without the frame change and check they are equivalent. Far likes this.

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July 24, 2014, 11:20		#3
khoopes Member Kevin Hoopes Join Date: Oct 2010 Posts: 43 Rep Power: 17	Thank you for your reply. Since I posted this yesterday I did a simulation with a split rotor and diffuser for comparison and the results look very similar. The metric that I am concerned with in this simulation was withing 0.5% which is fine for my application.