Heat Transfer in a pipe with different meshes

Using SimScale Thermal
2

Hey @Daniel_Koller,

First and foremost, welcome to the community!

That’s a nice validation project that you got going. When calculating the analytical solution, did you take into account that the flow gains temperature as it goes through the pipe? (i.e. heat transfer varies with temperature gradient)

For your questions:

  1. I can see both tet and hex meshes working well for this problem. Since the geometry (and the flow) are quite simple, with a hex mesh you would benefit from the alignment of flow/cell faces. But I’d say you should be able to get good results with either hex or tet;

  2. This is a very good question (and to be honest not enough people ask it). What you are doing is totally correct: a CFD project doesn’t consist of a single simulation. You should absolutely test different meshes and different configurations.
    The practitioner shouldn’t simply take the first converged simulation and assume it’s 100% correct. Just to give you an example, take a look at the number of runs that this NACA0012 verification project required.
    This topic is very broad but the short answer to it would be to follow the best practices and try to estimate the errors of your simulation runs. You can definitely find papers and books on error analysis and estimation in CFD. Just not to leave you hanging, I’ll refer you to Péric & Ferziger - Computational Methods for Fluid Dynamics - Chapter 11: Efficiency and Accuracy Improvement.

  3. For turbulent flows, you have to keep in mind the yplus requirements. But regardless of the type of flow, the near-wall-region often times will have bigger gradients and big gradients require more cells to be resolved appropriately.