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heat transfer problem between solid and fluid

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Old   November 6, 2019, 21:23
Default heat transfer problem between solid and fluid
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Song
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Dear all,

I`m performing a conjugate heat transfer problem. The heat is transferred from the solid to fluid. To conserve energy at the interface, I set a conservative interface flux in a heat transfer tree. After the simulation is done with transient mode, I got the result as shown in the figure attached.
My question is that the temperature at the interface between solid and fluid is high. However, the temperature distribution between solid and fluid is confined within the first cell in the fluid region.(between yellow lines) I expected a more smooth change at the interface.
Please tell me what is the problem with it. Thank you.
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Old   November 7, 2019, 02:03
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Mesh look coarse, but anyway results look reasonable, if flow is fast enough then it will efectively cool solid plate and flow twmpwrature remain moderate.
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Old   November 7, 2019, 16:29
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If you have not done a mesh sensitivity check then your results could be horribly inaccurate. Then you can easily get big jumps in temperature which are not real. Don't forget that you need to do sensitivity checks of time step size and convergence criteria as well.

If you are convinced your simulation is accurate then there are still reasons why a large jump in temperature could occur at the interface. One example is if this is a turbulent flow and you are using wall functions for heat transfer - then the first element in the fluid domain will be using the wall function value which represents a distance quite a way off the wall. This will appear as a jump in temperature.

Note you are ALWAYS going to get some jump at the interface as the element at the boundary in solid has a centroid a little way into the solid domain and the centroid of the first element in the fluid domain is a little way into the fluid domain. Any thermal gradients will then mean the temperatures in these adjacent elements will not be the same.

Finally - have a look in the documentation on hybrid and conservative values. This is related to this FAQ: https://www.cfd-online.com/Wiki/Ansy...t_the_walls.3F
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