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Discharge coefficient

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Old   March 29, 2023, 15:51
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 30, 2023, 00:51
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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 02:43.
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Old   March 30, 2023, 02:57
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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, 03:09
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Cd varies from 0.61 - 0.98, depending upon orifice entrance conditions
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Old   November 30, 2023, 06:23
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How to accurately determine Cd value.
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Old   December 1, 2023, 00:35
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most accurate method is physical model observations
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Old   May 6, 2024, 15:30
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The discharge coefficient is a dimensionless parameter used in fluid dynamics to describe the efficiency of a fluid flow through a constriction or an orifice. It represents the ratio of the actual flow rate to the theoretical maximum flow rate under the same conditions.
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Old   May 15, 2024, 13:44
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Venturi meters and other flow measurement devices rely on the relationship between pressure drop and flow rate. The discharge coefficient is used to correct for the effects of fluid viscosity, turbulence, and other factors on the accuracy of flow measurements.
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Old   June 3, 2024, 04:43
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Hello! To determine the coefficient of discharge (Cd) for a small hole in a large tank, you correctly use the formula Cd = Qflow3D/Qtheoretical, where Qflow3D is the actual flow rate you measured and Qtheoretical is the flow rate theory is calculated.
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