Discharge coefficient
 

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 ?

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.

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 :D )
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.

Cd varies from 0.61 - 0.98, depending upon orifice entrance conditions

How to accurately determine Cd value.

most accurate method is physical model observations

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.

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.