This presentation explains about the types, principle of operation and applications of Pitot tubes and Anemometer

1. PITOT TUBE, ANEMOMETER AND
THEIR TYPES

2. PRESSURE AND FLOW VELOCITY

3. PRESSURE
• Force applied perpendicular to the
surface of an object per unit area
over which that force is distributed
• Fluid pressure is most often the
compressive stress at some point
within a fluid
• Fluid pressure occurs in one of two
situations:
– An open condition, called "open
channel flow", e.g. the ocean, a
swimming pool, or the atmosphere.
– A closed condition, called "closed
conduit", e.g. a water line or gas line.
Pressure as exerted by
particle collisions inside
a closed container

4. Types of Pressures
• Closed bodies of fluid have two types
of pressure
1. Static pressure
2. Dynamic pressure

5. 1. STATIC PRESSURE
• Static pressure,
(hydrostatic pressure) is
the pressure of a fluid at
rest.
• Since the fluid is not
moving, static pressure is
the result of the fluid's
weight.

6. 2. DYNAMIC PRESSURE
• When a fluid is moving
through a pipe, there is a
second component to the
pressure. It is
called dynamic pressure.
• Dynamic pressure is a
pressure exerted
perpendicular to the
direction of the flow and
is represented by the
symbol q

7. TOTAL (STAGNATION) PRESSURE
• Stagnation pressure is equal to the sum of the
dynamic pressure and static pressure.
• The magnitude of stagnation pressure can be
derived from a simplified form of Bernoulli
Equation.
• For incompressible flow,
• 𝜌 is the fluid density,
• v is the velocity of fluid

8. TOTAL (STAGNATION) PRESSURE

9. PRESSURE MEASUREMENT
• Pressure measurement is the
analysis of an applied force by a
fluid (liquid or gas) on a surface.
• Pressure is typically measured in
units of force per unit of surface
area(example: N/m2 ,pound per
square inch (psi)).
• Many techniques have been
developed for the measurement
of pressure and vacuum.
Widely used Bourdon
pressure gauge

10. FLUID FLOW VELOCITY
• Flow velocity in fluid dynamics is a vector field
which is used to mathematically describe the
motion of a continuum.
• The length of the flow velocity vector is the
flow speed and is a scalar.
• The flow velocity u of a fluid,
• The flow speed q is the length of the flow
velocity vector is a scalar field.

11. FLUID FLOW VELOCITY
• .

12. PITOT TUBE

13. PITOT TUBE
• Also known as Pitot probe, is a
pressure measurement
instrument used to measure
fluid flow velocity.
• The pitot tube was invented
by the French engineer Henri
Pitot in the early 18th century
and was modified to its
modern form in the mid-19th
century by French scientist
Henry Darcy

14. WORKING PRINCIPLE
• The basic pitot tube consists of a tube
pointing directly into the fluid flow.
• As this tube contains fluid, a pressure can be
measured.
• The moving fluid is brought to rest (stagnates)
as there is no outlet to allow flow to continue.
This pressure is the stagnation pressure of the
fluid

15. WORKING PRINCIPLE

16. DETERMINATION OF AIR SPEED USING
STATIC AND DYNAMIC PRESSURE
• The dynamic pressure, then, is the difference
between the stagnation pressure and the static
pressure.
• The dynamic pressure is determined using a
diaphragm inside an enclosed container.
• The static pressure is generally measured using
the static ports on the side of the fuselage.
• The dynamic pressure measured can be used to
determine the indicated airspeed.

17. PITOT - STATIC TUBE
• Instead of separate pitot and
static ports, a pitot-static
tube (Prandtl tube) may be
employed, which has a
second tube coaxial with the
pitot tube with holes on the
sides, outside the direct
airflow, to measure the static
pressure

18. PITOT TUBE - APPLICATIONS

19. AIRCRAFT
• Pressure-sensitive instruments that is most
often used in aviation to determine an
1. aircraft's airspeed,
2. Mach number,
3. altitude, and
4. altitude trend.
• A pitot-static system generally consists of a
pitot tube, a static port, and the pitot-static
instruments.

20. AIRCRAFT
• Aircraft use pitot
tubes to measure
airspeed.
• The example, from
an Airbus A380,
combines a pitot
tube (right) with a
static port and an
angle-of-attack
vane (left).
• Air-flow is right to
left

21. ERRORS IN PITOT – STATIC SYSTEM
• Errors in pitot-static system
readings can be extremely
dangerous as the
information obtained from
the pitot static system, such
as airspeed, is potentially
safety-critical.
• Several commercial airline
incidents and accidents have
been traced to a failure of
the pitot-static system
Location of Pitot tubes on a
Boeing 777

22. AIRCRAFT ACCIDENTS DUE TO FAILURE OF
PITOT STATIC SYSTEM
• French air safety authority BEA said that pitot tube
icing was a contributing factor in the crash of Air
France Flight 447 into the Atlantic Ocean.
• In 2008 Air Caraïbes reported two incidents of pitot
tube icing malfunctions on its A330s.
• Birgenair Flight 301 had a fatal pitot tube failure which
investigators suspected was due to insects creating a
nest inside the pitot tube; the prime suspect is
the Black and yellow mud dauber wasp.
• Aeroperú Flight 603 had a pitot-static system failure
due to the cleaning crew leaving the static port blocked
with tape.

23. RACING CARS
• Used to compare the
speed of the air flow at
various locations of the
car to the real speed of
the car.
• Get an accurate
measurement of the true
speed of the car relative
to the air without that
measurement being
affected by the car’s own
movement through the
air

24. INDUSTIAL APPLICATIONS
• The flow velocities being measured are often
those flowing in ducts and tubing.
• In these, the most practical instrument to use
is the pitot tube.
• The pitot tube can be inserted through a small
hole in the duct with the pitot connected to a
U-tube water gauge or some other differential
pressure gauge for determining the flow
velocity inside the ducted wind tunnel.

25. INDUSTIAL APPLICATIONS
The fluid flow rate in a duct can then
be estimated from:
• Volume flow rate (cub. feet/min)
= Duct area (sq. feet) × flow
velocity (feet/min)
• Volume flow rate (cubic
meter/second)
= Duct area (Sq. metre) × flow
velocity(m/s)

26. ANEMOMETER

27. ANEMOMETER
• An Anemometer is a device
used for measuring the speed
of wind, and is also a common
weather station instrument.
• The term is derived from the
Greek word anemos, which
means wind
• Itis used to describe any wind
speed measurement
instrument used
in meteorology

28. HISTORY
• Leon Battista Alberti (1404–1472) is said
to have invented the first mechanical
anemometer around 1450.
• In 1846, John Thomas Romney
Robinson (1792–1882) improved upon
the design by using four hemispherical
cups and mechanical wheels.
• Canadian meteorologist John Patterson
developed a three-cup anemometer,
which was improved by Brevoort and
Joiner in 1935
• In 1991, Derek Weston added the ability
to measure wind direction

29. BASIC PARTS OF ANEMOMETER

30. BASIC WORKING PRINCIPLE

31. ANEMOMETER – TYPES

32. TYPES
• Anemometers are broadly classified into two
types,
1. Velocity anemometers
2. Pressure anemometers

33. I. VELOCITY ANEMOMETERS
• Cup anemometers
• Vane anemometers
• Hot-wire anemometers
• Laser Doppler anemometers
• Ultrasonic anemometers
• Acoustic resonance anemometers
• Ping-pong ball anemometers

34. 1. CUP ANEMOMETER(FOUR CUPS)
• It consisted of four hemispherical cups
mounted on horizontal arms, which
were mounted on a vertical shaft.
• Counting the turns of the shaft over a
set time period produced a value
proportional to the average wind
speed
• Cups are arranged symmetrically on
the end of the arms, the wind always
has the hollow of one cup presented
to it and is blowing on the back of the
cup on the opposite end of the cross

35. 1. CUP ANEMOMETER(THREE CUPS)
• Error of less than 3% up to 60 mph (97
km/h).
• Each cup produced maximum torque
when it was at 45° to the wind flow.
• The three-cup anemometer also had a
more constant torque and responded
more quickly to gusts than the four-
cup anemometer.
• Three-cup anemometers are currently
used as the industry standard for wind
resource assessment studies &
practice.

36. Where is this present?

37. 2. Vane Anemometers
• Windmill or a propeller anemometer.
• Axis parallel to the direction of the wind and therefore
horizontal.
• To align its direction to direction of air, a extra setup
such as wind vane is required
• A vane anemometer thus combines a propeller and a
tail
• Speed of the fan is measured by a rev counter and
converted to a windspeed by an electronic chip.
• Volumetric flowrate may be calculated if the cross-
sectional area is known.

38. 2. Vane Anemometers

39. 3. HOT WIRE ANEMOMETER
• Hot wire anemometers use a very
fine wire (in micrometres) electrically
heated to some temperature above
the ambient.
• Air flowing past the wire cools the
wire.
• Electrical resistance of most metals is
dependent upon the temperature of
the metal a relationship can be
obtained between the resistance of
the wire and the flow speed.

40. 3. HOT WIRE ANEMOMETER
• Extremely delicate, have extremely
high frequency-response and fine
spatial resolution compared to other
measurement methods, and as such
are almost universally employed for
the detailed study of turbulent flows
• An industrial version of the fine-wire
anemometer is the thermal flow
meter, which follows the same concept
but uses two pins or strings to monitor
the variation in temperature.

41. 4. LASER DOPPLER ANEMOMETER

42. 4. LASER DOPPLER ANEMOMETER
• A beam of light from a laser that is
divided into two beams, with one
propagated out of the anemometer.
• Particulates flowing along with air
molecules near where the beam exits
reflect, or backscatter, the light back
into a detector, where it is measured
relative to the original laser beam.
• When the particles are in great
motion, they produce a Doppler shift
for measuring wind speed in the laser
light, which is used to calculate the
speed of the particles, and therefore
the air around the anemometer.

43. 4. LASER DOPPLER ANEMOMETER
• A focusing device splits the laser into two beams,
which cross the flow at an angle 𝜃 .
• Light is scattered from a moving particle in the flow, a
stationary observer can detect a change, or doppler
shift, in the frequency of the scattered light.
• The shift f is proportional to the velocity of the
particle. If 𝜆 is the wavelength of the laser light, the
measured velocity is given by

44. 5. ULTRASONIC ANEMOMETER
• They measure wind speed based on
the time of flight of sonic pulses
between pairs of transducers.
• Ultrasonic anemometers can take
measurements with very fine
temporal resolution, 20 Hz or better,
which makes them well suited for
turbulence measurements
• Speed of sound varies with
temperature, and is virtually stable
with pressure change, ultrasonic
anemometers are also used as
thermometers.

45. 5. ULTRASONIC ANEMOMETER
• Lack of moving parts makes them appropriate for long-
term use in exposed automated weather stations and
weather buoys where the accuracy and reliability of
traditional cup-and-vane anemometers are adversely
affected by salty air or dust.
• Their main disadvantage is the distortion of the flow
itself by the structure supporting the transducers,
which requires a correction based upon wind tunnel
measurements to minimize the effect.
• Lower accuracy due to precipitation, where rain drops
may vary the speed of sound.

46. 5. ULTRASONIC ANEMOMETER
• Two ultrasounds paths: These sensors have 4
arms. The disadvantage of this type of sensor is
that when the wind comes in the direction of an
ultrasound path, the arms disturb the airflow,
reducing the accuracy of the resulting
measurement.
• Three ultrasounds paths: These sensors have 3
arms. They give one path redundancy of the
measurement which improves the sensor
accuracy and reduces aerodynamic turbulence

47. 6. ACOUSTIC RESONANCE ANEMOMETER
• Has cavity of an array of ultrasonic
transducers, which are used to
create the separate standing-wave
patterns at ultrasonic frequencies.
• As wind passes through the cavity, a
change in the wave’s property
occurs (phase shift).
• By measuring the amount of phase
shift in the received signals by each
transducer, and mathematically
processing the data, the sensor is
able to provide an accurate
horizontal measurement of wind
speed and direction.

48. 6. ACOUSTIC RESONANCE ANEMOMETER
• Acoustic resonance technology enables measurement
within a small cavity, the sensors therefore tend to be
typically smaller in size than other ultrasonic sensors.
• The small size of acoustic resonance anemometers
makes them physically strong and easy to heat and
therefore resistant to icing
• One issue with this sensor type is measurement
accuracy when compared to a calibrated mechanical
sensor.
• This weakness is compensated for by the sensor's
longevity and the fact that it does not require re-
calibrating once installed.

49. 7. PING-PONG BALL ANEMOMETER
• A common anemometer for basic use is
constructed from a ping-pong ball attached to a
string.
• When the wind blows horizontally, it presses on
and moves the ball; because ping-pong balls are
very lightweight, they move easily in light winds.
• Measuring the angle between the string-ball
apparatus and the vertical gives an estimate of
the wind speed.

50. II. PRESSURE ANEMOMETERS
The first designs of anemometers which
measure the pressure were divided into:
1. Plate and
2. Tube classes.

51. 1. PLATE ANEMOMETER
• First modern anemometers.
• Consist of a flat plate suspended
from the top so that the wind
deflects the plate.
• Later versions of this form
consisted of a flat plate, either
square or circular, which is kept
normal to the wind by a wind
vane.

52. 1. PLATE ANEMOMETER
• The pressure of the wind on its face is balanced
by a spring.
• The compression of the spring determines the
actual force which the wind is exerting on the
plate, and this is either read off on a suitable
gauge, or on a recorder.
• Instruments of this kind do not respond to light
winds, are inaccurate for high wind readings, and
are slow at responding to variable winds.
• Plate anemometers have been used to trigger
high wind alarms on bridges.

53. 2. TUBE ANEMOMETER
• The successful metal pressure tube
anemometer of William Henry
Dines in 1892
• Pressure difference between the
open mouth of a straight tube
facing the wind and a ring of small
holes in a vertical tube which is
closed at the upper end.
• Both are mounted at the same
height.
• The pressure differences on which
the action depends are very small,
and special means are required to
register them.
Tube anemometer by William
Henry Dines. The movable part
(right) is mounted on the fixed
part (left)

54. 2. TUBE ANEMOMETER
• The recorder consists of a float in a sealed
chamber partially filled with water.
• The pipe from the straight tube is connected
to the top of the sealed chamber and the pipe
from the small tubes is directed into the
bottom inside the float.
• The pressure difference determines the
vertical position of the float this is a measure
of the wind speed

55. PITOT TUBE STATIC ANEMOMETERS
• The implementation uses a pitot-static tube which is a
pitot tube with two ports, pitot and static.
• The pitot port measures the dynamic pressure of the
open mouth of a tube with pointed head facing wind,
and the static port measures the static pressure from
small holes along the side on that tube
• The pitot tube is connected to a tail so that it always
makes the tube's head to face the wind.
• Additionally, the tube is heated to prevent rime ice
formation on the tube

56. PITOT TUBE STATIC ANEMOMETERS
Instruments at Mount Washington Observatory.
The pitot tube static anemometer is on the right

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