{"id":162925,"date":"2021-10-08T13:07:44","date_gmt":"2021-10-08T13:07:44","guid":{"rendered":"\/forum\/forums\/topic\/mesh-study-heat-transfer-in-gap-flow\/"},"modified":"2021-10-15T07:38:30","modified_gmt":"2021-10-15T07:38:30","slug":"mesh-study-heat-transfer-in-gap-flow","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mesh-study-heat-transfer-in-gap-flow\/","title":{"rendered":"Mesh study heat transfer in gap flow"},"content":{"rendered":"
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Hello, <\/p>\n

I am simulating a 2D gap flow of air. The simulation is steady state, incompressible and the flow is laminar. The domain is 0.1 m long (x-dir) and 0.001 m wide (y-dir). At x=0 there is the inlet with a constant velocity and at x=0.1 m there is the outlet. At y=0 there is a wall and at y=0.001 m there is a symmetry BC. I am adding the energy equation. The temperature at the inlet is fixed with 293.15 K (20 °C) and and the wall it is set to be 283.15 K (10 °C). The mesh I am using has hexahedral nonuniform cells. I started with 300 cells in x-dir and 30 cells in y-dir (in total 9000 cells) and refined the mesh by increasing the amount of cells in both directions.<\/p>\n

I now compare the outlet temperature and the mean heat flux density at the wall between the different meshes. The outlet temperature I calculate as a mass flow weighted average at the outlet. For the heat flux density I take the heat transferred at the wall and divide it by the area of the wall interface.<\/p>\n

Neither the outlet temperature, nor the mean heat flux density seem to converge to a "constant" value. I increased the amount of cells until I hit 81.000 (900 x 90), which feels very fine to me. Residuals of the simulation are all great (<1e-9). I compared the mean heat flux density to correlations given in the VDI-Wärmeatlas and the absolute value seems to be fine (~ 1 % abbreviation).<\/p>\n

Any ideas why the solution does not converge to a "constant" value? Here is a plot of the mean heat flux density in dependency of the amount of cells used:<\/p>\n

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\n\"meanHeatFlowRateFluent.jpg\"
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