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very high pressure

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Old   January 14, 2022, 17:48
Default very high pressure
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Gabriel
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Hi, iīm simulating flow through a box with vents containing 6 spheres, what i donīt understand is that the results from the simulations shows very high pressure drop between inlet and outlet (42000 kinematic pressure at inlet and -10000 at outlet). is the simulation realistic?

simpleFoam case:
https://www.dropbox.com/s/pntr90nqtc...foam2.zip?dl=0
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File Type: png vmplayer_yETkoBGZ6I.png (38.1 KB, 27 views)
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Old   January 15, 2022, 10:33
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Yes, it makes sense. Look at the velocity and you'll see that you have a velocity of around 150m/s through each vent. So the (kinematic) dynamic pressure is Pd=0.5 * U^2 = 11,250. If we assume a loss coefficient of Cd=2 for the simple orifice, then that gives a dP of 22,500 per baffle, i.e. 44,500 between inlet and outlet. That matches the pressure you quoted.

The real question is: why do you have a hurricance passing through your vents? The answer: check your boundary condition. You are forcing in air at 6.68m/s at the inlet, and then this constructs do at the vents ... to 150m/s.

So, have a rethink about your BCs. The good news is that the code appears to be working nicely.
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Old   January 19, 2022, 19:49
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ok thanks for your answer
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