Absolutely calm atmosphere needed

Roman1 · March 1, 2023, 01:35

Hello all. There is a rectangular domain 20x40x12 m with a weak spring of the benzene vapour. The aim is to model the dispersion of benzene at the absolutely calm atmosphere (but with non-zero turbulence). I have tried a huge number of BC but failed with this task, because of the weak air currents that appear near the boundaries and at the corners. Their speed is about some centimeters per second but they are killing the process. Instead of descending to the ground (benzene has the density of 3,14), instead of penetrating through the boundary, instead of leaving the domain the benzene vapour goes up and curl and wirl ans so on. Please share your experience and help with a hint as of how to construct absolutely calm atmosphere. If it would be windy atmosphere or powerful spring of the vapour there would be no problems. Thanks.

Alczem · March 1, 2023, 05:31

Hey !

I have been looking for a similar setup for quite some time now, and I have not been able to achieve a perfectly still atmosphere (with sides and top patches open, and the bottom as the ground).

Out of curiosity, can you share the case ? I would like to see what boundary conditions you are using right now, and which solver.

To improve your velocities, you could maybe try to initialize the p and prgh with setExprFields and setExprBoundaryFields. I also had some success using the hydrostaticPressure function object to create a ph_rgh field used for the prghTotalHydrostaticPressure condition (normally only available in fireFoam). But I could not achieve a calm atmosphere with the regular totalPressure condition or zeroGradient if I have vertical and horizontal patches (it is way easier if you have only horizontal patches, like in a vertical pipe).

Good luck, I hope you find a solution

Roman1 · March 1, 2023, 15:03

This is the case. Most calm atmosphere through out the other results.

Roman1 · March 2, 2023, 13:25

Concerning of calm atmosphere I was wrong and bothered your. I tried to save time and resources and made great many obstacles to set smaller free space domain. A common rectangular domain works fine but requires some more cores. Thanks.

March 1, 2023, 01:35	Absolutely calm atmosphere needed	#1
Roman1 Member Roman Join Date: Sep 2013 Posts: 81 Rep Power: 12	Hello all. There is a rectangular domain 20x40x12 m with a weak spring of the benzene vapour. The aim is to model the dispersion of benzene at the absolutely calm atmosphere (but with non-zero turbulence). I have tried a huge number of BC but failed with this task, because of the weak air currents that appear near the boundaries and at the corners. Their speed is about some centimeters per second but they are killing the process. Instead of descending to the ground (benzene has the density of 3,14), instead of penetrating through the boundary, instead of leaving the domain the benzene vapour goes up and curl and wirl ans so on. Please share your experience and help with a hint as of how to construct absolutely calm atmosphere. If it would be windy atmosphere or powerful spring of the vapour there would be no problems. Thanks.

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March 1, 2023, 05:31		#2
Alczem Senior Member Join Date: Dec 2021 Posts: 204 Rep Power: 5	Hey ! I have been looking for a similar setup for quite some time now, and I have not been able to achieve a perfectly still atmosphere (with sides and top patches open, and the bottom as the ground). Out of curiosity, can you share the case ? I would like to see what boundary conditions you are using right now, and which solver. To improve your velocities, you could maybe try to initialize the p and prgh with setExprFields and setExprBoundaryFields. I also had some success using the hydrostaticPressure function object to create a ph_rgh field used for the prghTotalHydrostaticPressure condition (normally only available in fireFoam). But I could not achieve a calm atmosphere with the regular totalPressure condition or zeroGradient if I have vertical and horizontal patches (it is way easier if you have only horizontal patches, like in a vertical pipe). Good luck, I hope you find a solution

March 2, 2023, 13:25		#4
Roman1 Member Roman Join Date: Sep 2013 Posts: 81 Rep Power: 12	Concerning of calm atmosphere I was wrong and bothered your. I tried to save time and resources and made great many obstacles to set smaller free space domain. A common rectangular domain works fine but requires some more cores. Thanks.