VENTURI METER

1. Fluid Lab
khogr kamal
- VENTURI METER
Name: Khogr Kamal Ibrahim
Group: 1
Fluid lab.

2. Fluid Lab
khogr kamal
Experiment No. 2
Experiment Name : - VENTURI METER
Objectives
To measure the discharge and to investigate the characteristic of a Venturi
Meter.
Introduction
Flow meters are used in the industry to measure the volumetric flow rate of
fluids. Differential pressure type flow meters ( Head flow meters)measure flow
rate by introducing a constriction in the flow. The pressure difference caused
by the constriction is correlated to the flow rate using Bernoulli's theorem. If a
constriction is placed in a pipe carrying a stream of fuid,there will be an
increase in velocity,and hence an increase in kinetic energy ,at the point of
constriction.From an energy balance as given by Bernoulli’s theorem,there
must be a corresponding reduction in pressure.Rate of discharge from the
constriction can be calculated by knowing this pressure reduction,the area
available for flow at the constriction ,the density of the fluid and the
coefficient of discharge Cd. Coefficient of discharge is the ratio of actual flow
to the theoretical flow and makes allowances for stream contraction and
frictional effects. Venturi meter, orifice meter, and Pitot tube are widely used
head flow meters in the industry. The Pitotstatic is often used for measuring
the local velocity in pipes or ducts. For measuring flow in enclosed ducts or
channels

3. Fluid Lab
khogr kamal
Theory
Consider the flow of an incompressible fluid through the convergent-divergent
pipe shown in Fig.2. The cross-sectional area at the upstream section 1 is a1, at
the throat section 2 is a2, and at any other arbitrary section n is an. Piezometer
tubes at these sections register h1, h2, and hn as shown.
Assuming that there is no loss of energy along the pipe, and that the velocity and piezometric
heads are constant across each of the sections considered, then Bernoulli’s theorem states that
(P1/ρg) + (v1 /2g) + z = (P /ρg) + (v /2g) + z 2

4. Fluid Lab
khogr kamal
 Procedure
• The apparatus is located on the flat top of the hydraulic bench and the
instrument is properly levelled with the help of spirit level. • The water is
allowed to fill in the manometer tubes until all trapped air is removed • All
manometer tubes are checked properly connected to the corresponding
pressure taps are air-bubble free • The discharged valve is adjusted to a high
measureable flow rate. • After the level is stabilized, the water flow rate is
measured using volumetric method. • The pressure head for each point(total
six) is observed by the reading shown in monometer tube similarly the total
head at each point is observed with the help of hypodermic probe

5. Fluid Lab
khogr kamal
Calculation
pplying Bernoulli equations at section 1 and section 2, we get,
Q1=Q2
. . /
V1. =V2.
=
1- Q2 = 6.6* m^3/s
2- Q2 = 8.9* m^3/s
3- Q2 = 1.08* m^3/s

6. Fluid Lab
khogr kamal
Discussion:-
One of the disadvantages of orifice meters is the large irreversible pressure
loss across the orifice, which results in substantial pumping costs in case of
large diameter pipes. However, the same principle can be exploited with only
minimal pressure loss with the use of a Venture meter. In this case, the meter
consists of a section with both a smooth contraction and a smooth expansion.