pressure drop equation
 

Hi everybody,
Does someone know waht is the equation which is used in Fluent for the Pressure droplet??
I am using VOF scheme with air and water, and I calculated the Pressure drop by two different ways, one with an equation from a book talking about micro fluidic system and one other with Fluent . But when I calculate for a simple case (just a square channel) I do not find the same results. So maybe I do not take the same equation as Fluent!
Also, I looked for in the user's guide, but I found nothing.
If someone have a idea, let me know.
Regis

Hi Regis,
Even I need to find out the equation. If you get to know, kindly please send me a message.
Thanks!