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Discharge coefficient

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Old   March 29, 2023, 14:51
Default Discharge coefficient
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Mikolaj
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Hi everyone,
i'm trying to detemine discharge coefficient for simple problem - outflow of water from the large tank through small orifice.
After few trials i am getting Cd=0.8. Cd=Qflow3D/Qtheoretical

Any tips or suggestions ?
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Old   March 29, 2023, 23:51
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Sehroosh
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For finding out discharge coeffcient from model data, same orifice equation will work

Qmodel = Cd x A x sqrt(2gh)

Qflow3D/Qtheoretical works when Qtheoretical is determined without Cd.

Last edited by MSM1985; March 30, 2023 at 01:43.
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Old   March 30, 2023, 01:57
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Hi, thanks for reply.

I dont think i described the problem in detail.

I am trying to calculate Cd from equation Cd=Q_flow3D/(Asqrt(2gh)).
(in my mind A x sqrt(2gh) = Qtheoretical )
To get Q_flow3D and A(area) i am placing baffle (flux surface) in orifice.
To get h i am placing history probe.
BC Ymin,Ymax,Zmin -wall; Xmin-fluid elevation, Xmax-outflow, Zmax- fluid fraction 0


After that train of thought i am getting Cd around 0.8, i was hoping for 0,6-0,65.
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Old   March 30, 2023, 02:09
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Cd varies from 0.61 - 0.98, depending upon orifice entrance conditions
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Old   November 30, 2023, 05:23
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Rempel Jody
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How to accurately determine Cd value.
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Old   November 30, 2023, 23:35
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most accurate method is physical model observations
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Old   January 24, 2024, 01:09
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Mark Newton
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I have always wondered why it is not possible to make the maximum possible outflow of water? These are just my thoughts, nothing more.
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