[tehache]

Dear Foamers,


I am trying to simulate a process where several gases are mixing at a junction of several tubes using rhoReactingBuoyantFoam. Reactions are switched off. Temperatures are varying, prescribed on the outer walls. I thought I was all fine and set, when on a closer look I realized I have a region where temperature has local maxima. After a lot of experimenting with a lot of parameters and meshes I am pretty sure it is not a mesh, convergence criteria, or discretization scheme issue.

I have then tried thermos based on sensibleEnthalpy and on sensibleInternalEnergy, the result was that I got temperature maxima for both, but with different distributions.
Pressure is close to 1 atmosphere, temperature around 1300K, those maxima are some 20K above their surroundings (not limited to a cell, or few cells, its extended).
Mach number is small, around 0.003.


I do not have much experience with thermodynamics and gases and was, probably naively, expecting the same results from both approaches.


So my actual questions are:


1.) Those inner temperature maxima stay there even averaging over time, in a region where changes in kinetic energy are not big enough to account for this. Am I correct assuming that this should thermodynamically be impossible?


2.) Why can the use of sensibleEnthaly or sensibleInternalEnergy give different results,
and/or which of these formulations should be used in what cases?


thx a lot for any hints!