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diffusion effect opposite to convection

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Old   December 5, 2006, 07:59
Default diffusion effect opposite to convection
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hasan karabay
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Hi In a uniform flow field, I would like to see the diffusion effect opposite to convection.

To do so

I draw a square 1x1 with uniform 2d mesh I setup the left side as a velocity inlet with U velocity component =1 m/s V velocity component =10.5 m/s Constant temperature =300 K

Bottom Side velocity inlet with U velocity component =1 m/s V velocity component =10.5 m/s Constant temperature =300 K

Top Side velocity inlet with U velocity component =1 m/s V velocity component =10.5 m/s Constant temperature =2000 K

Right side Pressure outlet

Also I increased the heat conduction coefficient of the fluid to be able to see the diffusion effects (k/(rho*Cp)>>1 ). I just wanted to see temperature gradients opposite to flow direction.

I run the case. I have got the uniform velocity field but what ever I did I could not get any temperature gradient opposite flow direction. I have reduced velocities, increased the k and the temperature at the top. The temperature profile at the top swept out by convection.

However when I increased the temperature at the left side, I can get a temperature gradient perpendicular to flow direction.

Am I doing something wrong or these codes ignore the diffusion effect opposite the flow direction.

thanks

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