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Nozzles: Modeling the Discharge Coefficient

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Old   March 12, 2014, 12:41
Default Nozzles: Modeling the Discharge Coefficient
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Liam
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Hey Guys,

This is my first post on the forum but I am a regular reader since I started doing CFD modeling with Fluent. So I need help right now since I have been banging my head against the wall trying to figure this problem I have out.

My problem is that when I am modeling the discharge coefficient of a nozzle, I am getting different values for the discharge coefficient depending on where I take the pressure readings. I am taking presssure readings at the inlet, throat, outlet and sometimes farther downstream/upstream of the nozzle. These values sometimes will go above 1 which seems to be allright when I am also looking through a fluids textbook.

However, when I wish to find the pressure loss coefficient from this value, I am skeptical on the results. I have read many papers where they take the discharge coefficient and say that the pressure loss coefficient is (1/C^2) which can be done by rearranging the equation. But in doing this, I am getting values BELOW 1 and according to theory involving the pressure loss coefficient (or Euler Number), this cannot go below unity. I need help understanding where I am going wrong.

-Am I taking pressure readings in the nozzle at wrong locations?
-What if I am determining the pressure loss coefficient in a simple system rather then a nozzle? Where would I take the pressure readings for that?
-Is the "Euler Number" used to measure the pressure loss coefficient in any system?
http://en.wikipedia.org/wiki/Euler_number_(physics)

Any help will be appreciated! Thanks!
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discharge coefficient, euler number, nozzle, pressure loss coefficient

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