About Lesson
a. Free flow orifice:
- It is used to measure comparatively small streams.
- Consists of iron sheet, steel or aluminum plates that contain accurately machined circular opening or orifices usually ranging from 2.5 to 7.5 cm.
- The discharge through an orifice is calculated by the formula,
Q = 0.61 x 10-3 a
Where,
Q = discharge through orifice, l/s.
a = area of cross-section of orifice, cm2.
g = acceleration due to gravity
H = depth of water over the center of the orifice.
b. Sub-merged orifices:
- Sub-merged orifices may be divided into two types:
- Those having orifices of fixed dimension and
- Those in which the height of opening may be varied.
- The opening is sharp edged and usually rectangular, with the width being 2-6 times the height.
- Adjustable submerged orifices should be calibrated to obtain the discharge under varying head conditions.