convective flux calculation

Numerical methods and mathematical models of Elmer
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mark smith
Posts: 215
Joined: 26 Aug 2009, 18:20
Location: Peterborough, England

convective flux calculation

Post by mark smith »

Hi Elmer team
According to the models manual, using savescalars it is possible to write out the convective flux on a boundary using the following format

Solver 4
Exec solver = After timestep
Equation = SaveScalars
Procedure = "SaveData" "SaveScalars"
Filename = results.dat

Variable 1 = Temperature
Operator 1 = "convective flux"
Coefficient 1 = "Heat capacity"
End
I have been have some conversation with Dmitry under the subject of save scalars and the coefficient c in equation 44.6 seems to need to be density*heat capacity rather than just heat capacity as highlighted in the post
viewtopic.php?f=3&t=1177&p=3721&hilit=c ... 7c98#p3721

Now I am doing a scanning simulation where I vary the flow rate at the inlet and have a constant heatflux through a boundary, now the convective flux difference between the outlet and inlet should equal the heat flux irrespective of the flow rate (no other heat sources or sinks) but savescalars give significantly different results at different flow rates (all laminar flow)?

If I do the postprocessing in paraview and do the integral over the inlet/outlet boundary pair using density*heat capacity*normal_velocity*temperature then I get the expected result which equals the heatflux and is independent of the flow rate.

Questions : Am I using savescalars correctly to get the convective flux?
Is equation 44.6 correct if c= "Heat capacity" ?
What am I doing wrong?

Thanks in advance
Regards
Mark
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