This page calculates the head loss coefficient and head loss of a fluid in across a thin perforated plate (plate thickness / hole hydraulic diameter < 0.015) inside a pipe. It is assumed that Re is greater than 105.

The head loss hL can be calculated as:

hl = kloss x (um2 / (2 x g) )

Where kloss is the head loss coefficient, um is the flow velocity in the pipe, and g is the gravitational acceleration. kloss is calculated from:

kloss =

Where FAR is the free area ratio. The free area ratio must be entered directly by the user, but is defined as:

FAR = Free or Open Area / Total Area


Idel'chik, I E. and Fried, Erwin., Flow Resistance, a Design Guide for Engineers, Taylor & Francis, Washington D.C. 1989. p 260.