asking help for porous media simulation
 

I do the calculation, non-steady state, the porous medium model, two-dimensional rectangular grid, laminar flow, gas flow through from top to bottom, the upper material layer is cooled, the lower part is heated. Initially, the upper surface of the gas temperature at the same height cross section is the same, very flat. But over time, the gas temperature difference occurs at the same height. Actual physical process, at the same height position, the gas temperature should be the same. what is the problem , who can tell me?thank you so much!!!!!
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