wall heat flux 2D to 3D

Mat_fr · April 3, 2013, 05:35

Dear all,

I'm doing unsteady 2D computations of a heat transfer from a wall to my fluid, with a imposed heat flux. It is natural convection, with fluid density varying with temperature. I got relevant wall temperature (in comparison to theory).

In order to pursue my study, I tried a 3D case with the same numerical settings (cells size, controls, schemes). However, the temperature is here meaningless (10 times higher and osciallting a lot). The residuals are not as good as the 2D case, but it still seems to converge.

Of course the heat flux is the same in both cases. I computed the total power on the wall surface in Fluent, which is 120W.

Do you have any idea for the reason of the bad result with the 3D case ? If the mesh is enough fine in 2D, it should be ok for 3D !

Best,

Mat

vasava · April 3, 2013, 05:53

Is your 2D case axisymmetric?

Mat_fr · April 3, 2013, 12:39

No, its not 2D axisymmetric.
There is a plane of symmetry in the real geometry, and the 2D case is computed in this plane.

Mat_fr · May 2, 2013, 13:06

I'm really stuck with this problem.
Why I get different temperatures for the 2D and 3D cases, with the same power ? (160W) Knowing that for the 3D case, the temperatures are meaningless (really too high).

Thanks in advance for your help.

April 3, 2013, 05:35	wall heat flux 2D to 3D	#1
Mat_fr Member Mat Join Date: Jan 2012 Posts: 60 Rep Power: 14	Dear all, I'm doing unsteady 2D computations of a heat transfer from a wall to my fluid, with a imposed heat flux. It is natural convection, with fluid density varying with temperature. I got relevant wall temperature (in comparison to theory). In order to pursue my study, I tried a 3D case with the same numerical settings (cells size, controls, schemes). However, the temperature is here meaningless (10 times higher and osciallting a lot). The residuals are not as good as the 2D case, but it still seems to converge. Of course the heat flux is the same in both cases. I computed the total power on the wall surface in Fluent, which is 120W. Do you have any idea for the reason of the bad result with the 3D case ? If the mesh is enough fine in 2D, it should be ok for 3D ! Best, Mat

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April 3, 2013, 05:53		#2
vasava Senior Member Paritosh Vasava Join Date: Oct 2012 Location: Lappeenranta, Finland Posts: 732 Rep Power: 22	Is your 2D case axisymmetric?

April 3, 2013, 12:39		#3
Mat_fr Member Mat Join Date: Jan 2012 Posts: 60 Rep Power: 14	No, its not 2D axisymmetric. There is a plane of symmetry in the real geometry, and the 2D case is computed in this plane.

May 2, 2013, 13:06		#4
Mat_fr Member Mat Join Date: Jan 2012 Posts: 60 Rep Power: 14	I'm really stuck with this problem. Why I get different temperatures for the 2D and 3D cases, with the same power ? (160W) Knowing that for the 3D case, the temperatures are meaningless (really too high). Thanks in advance for your help.