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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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question about the obstacle in a wind channel

Posted 2011年3月18日 GMT-4 18:34 Version 3.5a 4 Replies

Kehui Chen
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Hi,

I am trying to find the air flow around the obstabcle in the wind channel, find the surronding velosity but there is some error.
Please help me remove this error

Thank you!

Best regards

Kehui Chen

Attachments:

4 Replies Last Post 2011年3月22日 GMT-4 11:11
Marcus Dahl
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Posted: 1 decade ago 2011年3月19日 GMT-4 18:24
Have you created a solid windtunnel? Is it the wing-like object in the middle that you want to model in a freestream?
In that case make a solid cube around the object, set the cube to air, the object to your chosen material and select two sides of the cube as inlet and outlet.


Have you created a solid windtunnel? Is it the wing-like object in the middle that you want to model in a freestream? In that case make a solid cube around the object, set the cube to air, the object to your chosen material and select two sides of the cube as inlet and outlet.
Kehui Chen
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Posted: 1 decade ago 2011年3月21日 GMT-4 15:56
YES, I want to model a wing-like object in the middle. I use the weakly compressible Navier- Stokes Module, and I made a solid cube around it and the inlet pressure is 0.2MPa and the outlet pressure is 0.1MPa, but when compute, there are some errors.

Exception:
com.femlab.jni.FlNativeException: Failed to evaluate expression
Messages:
Failed to evaluate expression
- Expression: d(((Lentr_chns*((-2*eta_chns*uTx+p)*test(uTx)-eta_chns*(uTy+vTx)*test(uTy)-eta_chns*(uTz+wTx)*test(uTz))-Pinl_chns*nx_chns*test(u)-h^2*(Lentr_chns*(pTx-eta_chns*(uTxx+uTyy+uTzz))+Pinl_chns*nx)*test(pTx)/(24*eta_chns))-(0))*(dvol),{test@1})

Failed to evaluate variable
- Variable: eta_chns
- Geometry: 1
- Boundary: 1

Stack trace:
at evaltree.cpp, row 866, ()
at xevalutil.cpp, row 2612, ()
at com.femlab.solver.FlSolver.femStatic(Native Method)
at com.femlab.solver.FemStatic.run(Unknown Source)
at com.femlab.server.FlRunner.run(Unknown Source)
at com.femlab.util.i.run(Unknown Source)
at com.femlab.util.aa.run(Unknown Source)
Please help remove thse errors.


Best regards!


Kehui Chen
YES, I want to model a wing-like object in the middle. I use the weakly compressible Navier- Stokes Module, and I made a solid cube around it and the inlet pressure is 0.2MPa and the outlet pressure is 0.1MPa, but when compute, there are some errors. Exception: com.femlab.jni.FlNativeException: Failed to evaluate expression Messages: Failed to evaluate expression - Expression: d(((Lentr_chns*((-2*eta_chns*uTx+p)*test(uTx)-eta_chns*(uTy+vTx)*test(uTy)-eta_chns*(uTz+wTx)*test(uTz))-Pinl_chns*nx_chns*test(u)-h^2*(Lentr_chns*(pTx-eta_chns*(uTxx+uTyy+uTzz))+Pinl_chns*nx)*test(pTx)/(24*eta_chns))-(0))*(dvol),{test@1}) Failed to evaluate variable - Variable: eta_chns - Geometry: 1 - Boundary: 1 Stack trace: at evaltree.cpp, row 866, () at xevalutil.cpp, row 2612, () at com.femlab.solver.FlSolver.femStatic(Native Method) at com.femlab.solver.FemStatic.run(Unknown Source) at com.femlab.server.FlRunner.run(Unknown Source) at com.femlab.util.i.run(Unknown Source) at com.femlab.util.aa.run(Unknown Source) Please help remove thse errors. Best regards! Kehui Chen
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2011年3月22日 GMT-4 02:37
Hi

I suspect you are missing a material property

--
Good luck
Ivar
Hi I suspect you are missing a material property -- Good luck Ivar
Zoran Vidakovic, COMSOL COMSOL Employee

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Posted: 1 decade ago 2011年3月22日 GMT-4 11:11
Hi Kehui

What you have imported are the solid bodies. So, you need actually the inverse geometry. Derive a domain for the fluid and apply the fluid flow physics there.
Checked model with v4.1...

Best regards,
Zoran
Hi Kehui What you have imported are the solid bodies. So, you need actually the inverse geometry. Derive a domain for the fluid and apply the fluid flow physics there. Checked model with v4.1... Best regards, Zoran

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