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Conduction Temperature Discontinuities in Flow Simulation without contact resistance

Question asked by John Bankert on May 31, 2017
Latest reply on Jun 6, 2017 by Joe Galliera



I am new to flow simulation, but have used Solidworks Simulation for a few years.  I am noticing some non-physical results when I look at temperature cut plots of mating solids.  To illustrate the results I made a simple simulation.  The setup is:


1) Two discs mated together without any contact impedance between them

2) External air flow, 1 m/s in plane with the discs.

3) Volumetric Heat source(1 W) imparted on one disc.

4) Material of the disc with the heat source has a conductivity of 1 W/mK

5) Material of the disc without the heat source has a conductivity of 100000 W/mK

6) 4 mesh elements through the thickness of the discs

7) Ambient temp 21 C



In the attached file "Single_Heat_Source_Compare.png", the temperature profile of a cut plot through the center of the discs is seen.  There is a clear discontinuity in the temperature at the junction between the two discs.  Unless I had specified a contact resistance, the second body's interface should should the same temperature as the mating part, and then the heat should diffuse appropriately.   In Solidworks Simulation thermal analysis, when you have two materials of different conductivities bonded together, as far as the solver is concerned they are a single body, and the impedance value simply changes between cells that belong to one part vs. another.  As such, a continuous solution is shown in Solidworks Simulation where the heat diffuses through the cells closest to the mating part.  As far as I understand, when there is no specified contact impedance between parts, there should never be a discrete temperature drop at the boundary.


Is there something I could have set up wrong to cause this?  Is the flow simulation program solving the mesh in a different way than I am imagining?  Thanks for the help!


P.S., out of curiosity I ran a simulation with power dumped into both discs, and the same issue happened.  I have attached some images showing another example with a completely different model (still no contact impedance), as well as some 1 D numerical integrations I did in matlab to illustrate how it should look with and without contact impedance for mated materials of different conductivities.  It bothers me that I am seeing these results and it makes me question the model I have.






Message was edited by: John Bankert Updated matlab plots