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Old   October 3, 2013, 22:03
Default errors in propeller simulation
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Dear all:

I tried to simulate profan at high speed, but there are some problems. The free stream is about 0.8 Ma. I calculated total pressure and total temperature as the inlet boundary condition. And I gave static pressure as outlet boundary condition. However, the result of static pressure at the inlet is much higher than I predicted. I used rotation domain and stationary boundary at both inlet and outlet.

And the temperature is also with errors. It looks like there is heat source at opening boundary. I am confused about that. Thank you for your suggestions.

Best,

Liu
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Old   October 4, 2013, 07:14
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FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

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I have no idea what your image is showing.
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Old   October 4, 2013, 22:33
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Dear ghorrocks;

Thank you for your reply.

Near the opening boundary, the temperature increased dramatically. And I calculated total temperature from inlet to outlet by mass flow average. I found that the total temperature increased continuously, even there's no blade in that domain. It seems like there is heat source at opening boundary.

Thank you
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File Type: jpg total temperature.jpg (72.5 KB, 10 views)
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Old   October 5, 2013, 06:23
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Do you have wall heat transfer? A hot wall could explain it.
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Old   October 5, 2013, 20:59
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All the wall boundaries are adiabatic. And I defined heat trasfer in fluid models as total energy.

Thank you.
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Old   October 6, 2013, 06:26
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I still do not knwo what you geometry looks like, what boundary conditions you applied or how you set this up. You will need to provide more details if we are to help.
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Old   October 6, 2013, 21:41
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Thank you for you reply.

In the picture I upload, the blue surface are blade and hub defined as no slip wall (adiabatic). Boundaries upstream and downstream are free slip wall. Inlet used total pressure and total temperature which I calculated from free stream Mach Number as boundary condition. Outlet used average static pressure. Opening defined as opening condition used velocity component (except axis direction, other two are zero). One of eight passages is calculated and the periodical boundary defined as rotational periodicity.

Best,

Liu
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Old   October 7, 2013, 06:11
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I can tell by the angularity in your contour lines in your first post that you are using a coarse mesh - so I would not trust the results from this simulation anyway. So I would do a mesh sensitivity study (and convergence, timestep and anything else) before I worried too much about the details of the results.
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Old   October 8, 2013, 02:57
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Thank you. I will try what you say
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