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Old   April 23, 2010, 06:54
Question Problem with axial alignment in Turbomachinery
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Wei Zhao
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Hi all,


I am new to ansys cfx. I want to simulate coaxial propellers used as helicopter main rotors. When I usually set up the boundary condition manually, but I always fail for this problem, so I tried the turbomachinery simulation type. But I got a frustrating problem in this process.


I set up four domains in the simulation, Inflow, upRotor, lowRotor, and Outflow (Figure 1). But when I perform the "Axial Alignment" (Figure 2), I found that the the S1 and S2 parts separate with the rotation parts (R1 and R2) (Figure 3). If I don't perform "Axial Alignment" and go on with the next step, the interfaces between S1/R1 and S2/R2 are not recognized automatically (Figure 4). The boundary condition is recognized as in Figure 5. If I just deleted these boundary conditions and set up the interface manually, everything is OK. But when I perform the simulation, I get an error as shown in Figure 6. Is there anyone could be of help with such problem? Thanks in advance.


The mesh size for S1 and S2 are as follows:
Global Mesh Setup: 500
Boundary and Inlet: 500
Interface: 20

The mesh size for R1 and R2 are as follows:
Global Mesh Setup: 100
Boundary: 30
Interface: 40
Mesh Blade: 30
Attached Images
File Type: jpg BeforeAlignment.jpg (93.2 KB, 24 views)
File Type: jpg AxialAlignment.jpg (90.0 KB, 13 views)
File Type: jpg AfterAlignment.jpg (94.2 KB, 12 views)
File Type: jpg interface.jpg (85.4 KB, 11 views)
File Type: jpg boundary.jpg (88.0 KB, 12 views)
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Old   April 23, 2010, 06:55
Default Figure 6
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Figure 6, Thanks.
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Old   April 26, 2010, 18:58
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Increase the stack size as the error message suggests. You do this at run-time (ie in solver manager or when you fire off the job from the command line).
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Old   April 28, 2010, 07:12
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Thanks very much, Glenn


I have changed the memory control / topology estimate factor to be 1.2. But I still got insufficient memory error. See the error in the figure and output file. I have found the link below:
http://www.kxcad.net/ansys/ANSYS_CFX.../i1379574.html
It seems that this will happen because of the windows 32 bit os. So, should I change it to be 64 bit version and increase the RAM?


Thanks
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File Type: txt MainRotor_001.out.txt (38.0 KB, 1 views)
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Old   April 28, 2010, 09:11
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Keep increasing the stack until it is happy.

But if you have to increase beyond about 1.5 then it means something is seriously wrong. Something in your simulation means the memory estimate is way wrong and is probably not working properly.
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Old   April 28, 2010, 10:09
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Thanks very much for your quick answer, Glenn. I have increased the memory control to be 2, but the error still exists. What do you think it will be the reason, mesh, domain interface set-up? Or should I try this another computer?


Thanks
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Old   April 29, 2010, 08:21
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There will be no difference on another computer. This problem comes up when the GGI is not working properly, or some other physics is not functioning correctly.
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Old   April 29, 2010, 09:11
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Glenn, Thanks very much, sincerely.
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Old   April 29, 2010, 09:25
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How many elements do you have in your simulation? Any how many RAM do you have? on 32bit, you can use about 2-2.3million element for 3GB RAM. (I was worked on a same project.)
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Old   April 29, 2010, 09:53
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I use a coarse mesh at present, so the total cells is about 800k, my desktop at present has 2GB RAM. I have not determined what is the problem.
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Old   April 29, 2010, 09:54
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Attesz is an unknown quantity at this point
800k should run on 2GB. There is other problem.
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Old   April 29, 2010, 11:32
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i think so too, thanks, Attila.
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Old   May 4, 2010, 05:14
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Glenn,

u r completely right. the memory control is not defined properly, thanks.
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