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Loss Coefficient for Opening Boundary Condition

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Old   March 7, 2015, 18:15
Default Loss Coefficient for Opening Boundary Condition
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Liliane Maciel
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Hello everybody,

I haven't realized yet if the loss coefficient (f) used by CFX is the same of the loss coefficient (\zeta) I have seen in other references. I have the opening discharge coefficient value and I have to set the loss coefficient in CFX, but I am not sure how those coefficients are related.Here is what I found in the Ansys Help:
You can optionally specify a Loss Coefficient which can be used to model the pressure drop across a screen or other planar resistance at the opening. The pressure drop is calculated using:

\Deltap _{loss} = \frac{1}{2} f \rho Unē

where f is a specified Loss Coefficient and Un is the normal component of velocity at the opening boundary location.
and the relation I found in some papers between discharge coefficient (Cd) and loss coefficient (\zeta) is the following:
Cd = \frac{1}{\sqrt{\zeta}}

Is \zeta and f the same?

Last edited by Liliane Maciel; March 9, 2015 at 07:38.
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