Why is the pressure larger than the total pressure

greatwall · November 9, 2012, 04:41

I am simulating a gas flow through a rotating multi-channels with CFX, both the inlet and outlet are the Opening boundary condition. While the inlet has a reletive pressure of 4atm, and the outlet of 2atm, rotation speed is 10000r/min. When I look the result of my computation, at the inlet plane, the pressure is larger than the total pressure, how could this happened?

ghorrocks · November 9, 2012, 05:30

Can you show some images of what you are seeing?

greatwall · November 9, 2012, 06:07

[IMG]
These are the inlets, the range of the contour is local, from the picture we can see that the pressure is larger than the total pressure in the inlets plane, I don't know why.

ghorrocks · November 9, 2012, 06:09

Sorry, I do not download files from other websites. Please post them as attachments to this post (using "Go Advanced").

greatwall · November 9, 2012, 06:12

[IMG]http://b323.photo.store.qq.com/psb?/V13rxVKa3rhjqK/dwmy9NgB8guQ2FZrPtVmGUFOOzoOhbMyE*ps3QsggBA!/b/dGl*isCnAAAA&bo=hAOAAQAAAAADACM![/IMG]

greatwall · November 9, 2012, 06:24

1.jpg

2.jpg

ghorrocks · November 9, 2012, 06:36

We will need to see a bit more of the geometry to make any sense of it. Can you post an image which shows what the flow is actually doing?

Also, is this boundary on a rotating frame of reference? Multiphase? Does it have reverse flow?

greatwall · November 9, 2012, 06:51

This boundary is on a rotating frame of reference, no multiphase. The geometry is a turbine blade internal cooling channel, in the computation, the trailing edges did have reverse flow.
3.jpg

ghorrocks · November 9, 2012, 16:22

Where is the axis of rotation for the domain?

greatwall · November 9, 2012, 21:36

The axis of the rotation is on the negative y direction

ghorrocks · November 11, 2012, 06:10

I see. I cannot explain what you are seeing.

What does the total pressure in the stationary frame of reference look like?

greatwall · November 12, 2012, 21:49

The problem has been solved. Thank you! When I put the total pressure in the stationary frame of reference, the result is correct.

November 9, 2012, 04:41	Why is the pressure larger than the total pressure	#1
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	I am simulating a gas flow through a rotating multi-channels with CFX, both the inlet and outlet are the Opening boundary condition. While the inlet has a reletive pressure of 4atm, and the outlet of 2atm, rotation speed is 10000r/min. When I look the result of my computation, at the inlet plane, the pressure is larger than the total pressure, how could this happened?

November 9, 2012, 06:07		#3
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	[IMG] These are the inlets, the range of the contour is local, from the picture we can see that the pressure is larger than the total pressure in the inlets plane, I don't know why. Last edited by greatwall; November 9, 2012 at 06:12. Reason: the pictures didnot show well

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November 9, 2012, 05:30		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Can you show some images of what you are seeing?

November 9, 2012, 06:09		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Sorry, I do not download files from other websites. Please post them as attachments to this post (using "Go Advanced").

November 9, 2012, 06:12		#5
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	[IMG]http://b323.photo.store.qq.com/psb?/V13rxVKa3rhjqK/dwmy9NgB8guQ2FZrPtVmGUFOOzoOhbMyEps3QsggBA!/b/dGlisCnAAAA&bo=hAOAAQAAAAADACM![/IMG]

November 9, 2012, 06:24		#6
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	1.jpg 2.jpg

November 9, 2012, 06:36		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	We will need to see a bit more of the geometry to make any sense of it. Can you post an image which shows what the flow is actually doing? Also, is this boundary on a rotating frame of reference? Multiphase? Does it have reverse flow?

November 9, 2012, 06:51		#8
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	This boundary is on a rotating frame of reference, no multiphase. The geometry is a turbine blade internal cooling channel, in the computation, the trailing edges did have reverse flow. 3.jpg

November 9, 2012, 16:22		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Where is the axis of rotation for the domain?

November 9, 2012, 21:36		#10
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	The axis of the rotation is on the negative y direction

November 11, 2012, 06:10		#11
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	I see. I cannot explain what you are seeing. What does the total pressure in the stationary frame of reference look like?

November 12, 2012, 21:49		#12
greatwall New Member Join Date: Apr 2011 Posts: 8 Rep Power: 15	The problem has been solved. Thank you! When I put the total pressure in the stationary frame of reference, the result is correct.