Rotating wall

Dav3dum · January 8, 2019, 09:44

Hello everyone!

I'm currently working on a comparison of rotating wall boundary condition vs Moving Refence Frame on an electrical machine. My question is that can anyone tell me how does the rotating wall appear in the solved equations?

Thanks in advance,
David

LuckyTran · January 10, 2019, 10:08

I just want to point out that rotating wall and moving reference frame are completely independent of one another and you need to be careful you are interpreting your results correctly.

In the stationary frame with stationary walls you solve something. Now you set the wall rotating, which just means you give the wall a velocity. So the fluid next to the wall, due to no slip, instead of having velocity = 0, now has velocity same as the moving wall.

In a moving reference frame, your velocity is now completely redefined. A not-moving wall in the stationary frame now has a funny looking velocity in the moving reference frame (because your velocity has been redefined). So here you need to be careful what you mean by non-rotating vs rotating in either frame. It is a problem of semantics/English at this point.

January 8, 2019, 09:44	Rotating wall	#1
Dav3dum New Member Join Date: Jul 2016 Posts: 4 Rep Power: 10	Hello everyone! I'm currently working on a comparison of rotating wall boundary condition vs Moving Refence Frame on an electrical machine. My question is that can anyone tell me how does the rotating wall appear in the solved equations? Thanks in advance, David

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January 10, 2019, 10:08		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,747 Rep Power: 66	I just want to point out that rotating wall and moving reference frame are completely independent of one another and you need to be careful you are interpreting your results correctly. In the stationary frame with stationary walls you solve something. Now you set the wall rotating, which just means you give the wall a velocity. So the fluid next to the wall, due to no slip, instead of having velocity = 0, now has velocity same as the moving wall. In a moving reference frame, your velocity is now completely redefined. A not-moving wall in the stationary frame now has a funny looking velocity in the moving reference frame (because your velocity has been redefined). So here you need to be careful what you mean by non-rotating vs rotating in either frame. It is a problem of semantics/English at this point.