# question on simulating rotating channel with a pressure gradient

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 January 14, 2014, 08:35 question on simulating rotating channel with a pressure gradient #1 Senior Member   Huang Xianbei Join Date: Sep 2013 Location: Yangzhou,China Posts: 302 Rep Power: 13 hi everyone I'm doing a simulation on the rotating channel in which the water is driven by pressure gradient. I think it's reasonably to use momentum source to implement the pressure gradient for the dimension of pressure gradient is just the same as the momentum source, kg m^-2 s^-2. The channel is rectangular and the rotating axis is set at the center of the left face where x=0, the x direction is the streamwise ,and the z axis is the rotating axis, y is spanwise. z and x direction are set with 2 pairs of periodic interfaces to make the flow fully developed. However, the results shows no asymmetry aross the y direction and the speed in the x direction is far away from expected, is this method wrong or in other words, no suitable in this problem?

 January 14, 2014, 16:57 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,749 Rep Power: 143 Please post an image of what you are modelling and an image of what you are seeing in the results. Accuracy is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

January 14, 2014, 21:45
#3
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Huang Xianbei
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Quote:
 Originally Posted by ghorrocks Please post an image of what you are modelling and an image of what you are seeing in the results. Accuracy is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
[IMG]C:\Users\dodo\Desktop\QQ截图20140115104055.png[/IMG]
the calculation domain is as the image shows[IMG]C:\Users\dodo\Desktop\QQ截图20140115104337.png[/IMG]
here is the result, it's interesting to find that the slop of the calculation curve is the same as the slop in theory, but the y axis U is about 20 time larger than the theory

 January 14, 2014, 21:50 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,749 Rep Power: 143 The attached images did not work, please try again.

January 14, 2014, 21:53
#5
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Huang Xianbei
Join Date: Sep 2013
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Quote:
 Originally Posted by ghorrocks The attached images did not work, please try again.
Hi, ghorrocks
I tried to submit my image, while only the URL can be used. Is it impossible to use local file in my computer?

 January 14, 2014, 22:04 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,749 Rep Power: 143 No, you cannot see files on your local computer over the web. Not unless your PC is a web server that is You will have to upload it to the forum.

January 14, 2014, 22:39
#7
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Huang Xianbei
Join Date: Sep 2013
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Quote:
 Originally Posted by ghorrocks No, you cannot see files on your local computer over the web. Not unless your PC is a web server that is You will have to upload it to the forum.

the non-dimensional velocity U is done by u/ut， u is the dimensional velocity and ut is the friction velocity which is a constant, in the tunnel flow theory, the slope of the U curve is about -2w, y is the non-dimensional variable which implies the y direction,y=-1 and +1 refers to suction side and pressure side of the channel.

The second picture is the calculation domain of the tunnel, the flow is in the x direction and the whole tunnel rotates with z axis which is set at the center of the left side of x direction surface. Both the x and z direction were set with a pair of translational periodic interfaces.

 January 14, 2014, 22:41 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,749 Rep Power: 143 I have no idea what the diagram means, what the graph is of and what your flow is. Please put some description on your images so we can understand it.

 January 14, 2014, 22:50 #9 Senior Member   Huang Xianbei Join Date: Sep 2013 Location: Yangzhou,China Posts: 302 Rep Power: 13 here is the results of DNS, and the condition I chose is Ro=0.5, it's obvious that the U is far away from the DNS results

 January 14, 2014, 22:53 #10 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,749 Rep Power: 143 You still have not explain what the graph is and what the diagram means. I just see a box.

January 14, 2014, 23:00
#11
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Huang Xianbei
Join Date: Sep 2013
Location: Yangzhou,China
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Quote:
 Originally Posted by ghorrocks I have no idea what the diagram means, what the graph is of and what your flow is. Please put some description on your images so we can understand it.
Hi ,ghorrocks

Thank you for your advise. I tried my best to explain the problem now, if there is any misunderstanding, I'll go on to explain more details