®
V e n t u r i A p p a r a t u s
0 1 2 -0 9 4 8 6 B
I n t r o d u c t i o n
4
Introduction
In the Venturi Apparatus, air or water flows through a channel of varying width. As
the cross-sectional area changes, volumetric flow rate remains constant, but the veloc-
ity and pressure of the fluid vary. With a Quad Pressure Sensor connected to the
built-in Pitot tubes, the Venturi Apparatus allows the quantitative study and verifica-
tion of the Continuity Equation, Bernoulli’s principle, and the Venturi effect.
The model ME-8598 Venturi Apparatus includes the connectors and tubing needed
for doing the experiment with either air or water. This manual contains complete
experiment instructions, including several options for fluid supply and flow-rate mea-
surement.
Theory
An incompressible fluid of density
ρ
flows through a pipe of vary-
ing diameter (see Figure 1). As the cross-sectional area decreases
from A
0
(large) to A (small), the speed of the fluid increases from
υ
0
to
υ
.
The flow rate, R, (volume/time) of the fluid through the tube is
related to the speed of the fluid (distance/time) and the cross-sec-
tional area of the pipe. The flow rate must be constant over the
length of the pipe. This relationship is known as the Continuity
Equation, and can be expressed as
(eq. 1)
R
=
A
0
υ
0
=
A
υ
As the fluid travels from the wide part of the pipe to the constriction, the speed
increases from
υ
0
to
υ
, and the pressure decreases from P
0
to P. If the pressure
change is due only to the velocity change, Bernoulli's Equation can be simplified to:
(eq. 2)
Experiment
This experiment can be conducted with either air or water. Appendix B contains
equipment lists and instructions specific to each method.
Note: You can use a PASPORT interface (or interfaces) connected to a computer running
DataStudio software or on an Xplorer GLX interface in standalone mode (without a computer).
For instructions on collecting, graphing, and analyzing data, press F1 to open DataStudio on-line
help, or see the Xplorer GLX Users’ Guide.
Pre-Setup Measurements
Remove the top plate from the apparatus. Measure the depth of the channel and the
widths of the wide and narrow sections. Calculate the largest cross-sectional area (A
L
)
and the smallest cross-sectional area (A
S
).
P
A
u
P
0
A
0
u
0
Figure 1: Fluid flow through a pipe of varying
diameter
P
P
0
1
2
---
ρ υ
2
υ
0
2
–
(
)
–
=
