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Solar updraft tower flow going upside down

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Old   May 6, 2023, 11:59
Default Solar updraft tower flow going upside down
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Irene
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Hi everyone,
I am trying to simulate the flow inside a solar chimney in Converge, but, as the title says, I am having some issues regarding the direction of the flow. The air is supposed to exit the top of the chimney because of natural convection, but, instead it enters from the top and exits from the bottom.


My boundary conditions are:


Stack: Zero normal gradient
Collector: Zero normal gradient
Absorber (the ground): Heat flux (-1000 W/m2)
Inlet: 101325 Pa
Outlet: 101325 Pa


The chimney is 2m high and the collector has a 1,5 radius. I got both geometry and boundary conditions from papers and I am not really able to understand what's going wrong. I've also tried to force a positive velocity on the outflow in order to see if a delta pressure is needed given that I am expecting more or less a 2m/s velocity, but, when I substitute the pressure value I get (which is 101315 Pa) and run the simulation again, velocity is still directed towards the ground.


I've attached some really raw postprocessing in paraview showing density, temperature and flow direction. I've also added buoyancy and gravity in my simulation and I am running a steady-state case, compressible with only air.
Hopefully someone could help. Thanks in advance!
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File Type: jpg pressure.jpg (22.7 KB, 12 views)
File Type: jpg density.jpg (25.2 KB, 11 views)
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Old   May 31, 2023, 10:32
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Ameya Waikar
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Hello, can you please send the case setup to support@convergecfd.com, we can definitely look further into this. Thank you.
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converge case setup, flow direction, greenhouse effect, natural convection, solar chimney

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