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On the turbulent model and erengy loss

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Old   March 18, 2003, 04:41
Default On the turbulent model and erengy loss
  #1
Raintung
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Hello everyone,

When I use fluent to simulate 3D flow field in compressor (k-epsilon model), I find the energy loss is larger than the test results. What¡¯s the reason? Do the different turbulent model have different effects on the losses? What should I do? Thank you!
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Old   March 20, 2003, 04:53
Default Re: On the turbulent model and erengy loss
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Chetan Kadakia
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Turbulence is modeled, not solved with exact equations, and CFD solutions are only so accurate.

Run your solution with a refined mesh and see what happens.

Also try other models like RSM.

Give exact details, and I will give you specific suggestions.
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Old   March 20, 2003, 09:11
Default Re: On the turbulent model and erengy loss
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Raintung
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Thank you!

I am simulating the simple flow in the stationary cascade of axial compressor. The coarse mesh is semi-structured. Boundary conditions: inlet total pressure: 101920, total temperature: 292K; outlet pressure: 100325.

I select the standard k-epsilon model, but find the boundary layer near to the suction surface is thicker in the process of the postprocessing and the energy loss coefficient(on a plane vertical to the axis) is larger than the test results. The formula: Energy loss coef.=1-(1-(p/ptotal)**((r-1)/r))/(1-(p/101920) **((r-1)/r))

Hope your advice! With many thanks, raintung.
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Old   March 20, 2003, 10:08
Default Re: On the turbulent model and erengy loss
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prakashsrivastava
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sir hope that this mail finds u in best of u r mood. i m an analyst workin on analysis software.i m keen interested in ur turbulent & energy loss model plz send me this on my e mail

thanking u
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Old   March 20, 2003, 17:54
Default Re: On the turbulent model and erengy loss
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Chetan Kadakia
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Refine your boundary layer, and areas of higher pressure gradients.
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Old   March 22, 2003, 07:01
Default Re: On the turbulent model and erengy loss
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Raintung
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Hello , Thank you for your message (cfd-online). I would like to exchange experience with you on the turbulence &energy loss. I am simulating the simple flow in the stationary cascade of axial compressor, which is one of my examples. And the experiment was made under the same conditions. Now, I only employ the coarse mesh in order to decide which model is suitable to the example. According to the test results, the contour of energy loss coef. concentrate near to the suction surface(on a plane vertical to the axis). However, in the computation results, the loss value is larger and the boundary layer is thicker at the same stations, though I use the same formula. Now I use the k-epsilon standard model, and I don¡¯t know whether the different turbulent model will have different effect on the losses. I am sorry of my poor writing and afraid you can¡¯t understand me clearly. Maybe you know this very well and I hope your advice. Thank you!
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