1
CE 321
INTRODUCTION TO FLUID MECHANICS
Fall
2009
LABORATORY 5: CALIBRATION OF WEIRS
PURPOSE
To observe freesurface flow over a sharp–crested weir and to measure depth
and discharge over the weir.
OBJECTIVE
To establish a depthdischarge relation for a Vnotch weir.
EQUIPMENT REQUIRED
Hydraulic bench with Vnotch weir, hook gage and stopwatch
BACKGROUND
Read sections 10.6.2 and 10.6.3 (pp. 397401) in the text. The section describes
weirs and their uses for flow measurements; in particular, the theoretical development
of the sharpcrested weir. Beginning with the Bernoulli relation and subsequently
accounting for nonideal flow conditions, a correlation between discharge and a
representative water depth Y can be derived for the Vnotch weir:
2
5
2
tan
2
15
8
Y
g
C
Q
d
=
θ
(1)
Where:
Q is the discharge or flow over the weir
θ
is the angle of the vee in the weir
C
d
is the discharge coefficient for the given weir.
Y is the height of the water measured from the bottom of the vee to the free
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 Spring '08
 Mantha,P
 Fluid Dynamics, Fluid Mechanics, Flow control, Weir

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