Civil Engineering Department

EUROPEAN UNIVERSITY of LEFKE
Faculty of Engineering
Civil Engineering Department
Hydraulics Lab Manual
2015

1
Bernoulli’s Theorem Exercise
Description
The test section is an accurately machined clear acrylic duct of varying circular cross section. It
is provided with a number of side hole pressure tappings which are connected to the manometers
housed on the rig. These tappings allow the measurement of static pressure head simultaneously
at each of 6 sections. To allow the calculation of the dimensions of the test section, the tapping
positions and the test section diameters are shown on the following diagram:
Bernoulli’s Theorem Exercise
2
The dimensions of the tube are detailed below:

Note: the assumed datum position is at tapping A associated with h1.
The test section incorporates two unions, one at either end, to facilitate reversal for convergent or
divergent testing.
A hypodermic, the total pressure head probe, is provided which may be positioned to read the
total pressure head at any section of the duct. This total pressure head probe may be moved after
slackening the gland nut; this nut should be re-tightened by hand. To prevent damage, the total
pressure head probe should be fully inserted during transport/storage. An additional tapping is
provided to facilitate setting up. All eight pressure tappings are connected to a bank of pressurised
manometer tubes. Pressurisation of the manometers is facilitated by removing the hand pump
from its storage location at the rear of the manometer board and connecting its flexible coupling
to the inlet valve on the manometer manifold.
In use, the apparatus is mounted on a base board which is stood on the work surface of the bench.
This base board has feet which may be adjusted to level the apparatus. A level glass is provided
as part of the base.
The inlet pipe terminates in a female coupling which may be connected directly to the bench
supply. A flexible hose is attached to the outlet pipe, which should be directed to the volumetric
measuring tank on the hydraulics bench.
A flow control valve is incorporated downstream of the test section. Flow rate and pressure in
the apparatus may be varied independently by adjustment of the flow control valve, and the bench
supply control valve.
Objective
To investigate the validity of the Bernoulli equation when applied to the steady flow of water in
a tapered duct.
Method
To measure flow rates and both static and total pressure heads in a rigid convergent/divergent
tube of known geometry for a range of steady flow rates.
Equipment
In order to complete the demonstration of the Bernoulli apparatus we need a number of pieces of
equipment.
Bernoulli’s Theorem Exercise
3

Theory – The Bernoulli Equation
The Bernoulli equation represents the conservation of mechanical energy for a steady,
incompressible, frictionless flow: