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-   -   Has the kind of mesh influence on the solving method used by software? (http://www.cfd-online.com/Forums/star-ccm/98487-has-kind-mesh-influence-solving-method-used-software.html)

fshak92 March 12, 2012 11:07

Has the kind of mesh influence on the solving method used by software?
 
1) In a conjugate heat transfer case for finding the HTC and LocalHTC I've meshed my model(a body surrounded by air) in two ways(first polyhedral and second Trimmer).
There isn't any velocity and i've used the segregated solver and all the conditions are same for both cases.
In trimmer case Just the energy equation is solved but for polyhedral, the momentum and continuity equations are solved as well.
I wonder if someone tells me how the kind of mesh influences on solving equations in my case.

2)And also do you know how Heat transfer coefficient and LocalHTC are calculated by the software? the tutorial hasn't explained in a good way.

Thank you in advance.

siara817 March 13, 2012 13:35

How was the quality of the mesh for the both cases?
If the quality of the mesh is low in any case, then the solution will not converge.
I hope you know how to check for example Cell quality in STAR CCM.
Good luck

MFitl March 14, 2012 03:07

Quote:

Originally Posted by omid88 (Post 348956)
1)

2)And also do you know how Heat transfer coefficient and LocalHTC are calculated by the software? the tutorial hasn't explained in a good way.

The definition of the HTC is:

\alpha = \frac{\Delta T}{\Delta Q} = \frac{T - T_{ref}}{\Delta Q}

Depending on T_{ref} the \alpha is different for the same \Delta Q.

For the HTC T_{ref} is the temperature you need to set in Tools|FieldFunctions|Heat Transfer Coefficient.

For the LocalHTC T_{ref} is the local temperature of the cell next to the wall.

abdul099 March 15, 2012 04:27

The solver should do the same for both meshes. Can you create a summary report on both cases and compare them for different settings (apart from mesh settings)?

fshak92 March 15, 2012 08:02

Thank you all for your answers:)

To Abdul099 : Firstly i set some constant temperature on the body as a heat source and let the wall be adiabatic(i know its not realistic) and the above mentioned problem was occured. but after setting some constant temperature to the wall , both of poly and trimmer behave in a same way and just an energy eqation is solved(not Momentum and Continuity).I dont know why in first case the difference in solution method was seen...

To Siara817: Thank you for your explanation but i cannot understand exactly the meaning of 'the local temperature of the cell next to the wall'. Because in spite of same reference temperature with the wall temperature,,the LHTCs are 1000times more than HTCs.

Again Thank you all for your considerations.


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