The document provides an overview of fluid flow measurement, detailing various types of flow (laminar, turbulent, and transient) and their characteristics, as well as historical developments in flow measurement techniques. It discusses the significance of Reynolds number in determining flow type and defines key concepts such as mass flow rate and volume flow rate. Additionally, it describes various flow measurement principles, specifically focusing on differential pressure flow meters and their applications, including orifice plates and their components.

1. Flow
Measurement(basics)
Ashvani Shukla
C&I
Reliance

2. INTRODUCTION
• In the physical world, mechanical engineers are frequently
required to monitor or control the flow of various fluids through
pipes, ducts and assorted vessels. This fluid can range from thick
oils to light gasses. While some techniques work better with some
groups of fluids, and less well with others, some are not at all
suitable for some applications. In this primer on fluid flow
instrumentation we will look at a wide variety of flow transducers
and their application in the physical world.

3. Fluid flow measurement
• Fluid flow measurement can encompass a wide variety of fluids and
applications. To meet this wide variety of applications the instrumentation
industry has, over many years, developed a wide variety of instruments. The
earliest known uses for flow come as early as the first recorded history. The
ancient Sumerian cities of UR and Kish, near the Tigris and Euphrates rivers
(around 5000 B.C.) used water flow measurement to manage the flow of water
through the aqueducts feeding their cities. In this age the a simple obstruction
was placed in the water flow, and by measuring the height of the water flowing
over the top of the obstruction, these early engineers could determine how
much water was flowing. In 1450 the Italian art architect Battista Alberti
invented the first mechanical anemometer. It consisted of a disk placed
perpendicular to the wind, and the force of the wind caused it to rotate. The
angle of inclination of the disk would then indicate the wind velocity. This was
the first recorded instrument to measure wind speed. An English inventor,
Robert Hooke reinvented this device in 1709, along with the Mayan Indians
around that same period of time. Today we would look down our noses at these
crude methods of flow measurement, but as you will see, these crude methods
are still in use today.

4. TYPE OF FLOW
• There are in general three types of fluid flow in pipes
• laminar
• turbulent
• transient
• Laminar flow
• Laminar flow generally happens when dealing with small pipes and low flow
velocities. Laminar flow can be regarded as a series of liquid cylinders in the pipe,
where the innermost parts flow the fastest, and the cylinder touching the pipe isn't
moving at all.
• Shear stress in a laminar flow depends almost only on viscosity - μ - and is
independent of density - ρ.
• Turbulent flow
• In turbulent flow vortices, eddies and wakes make the flow unpredictable.
Turbulent flow happens in general at high flow rates and with larger pipes.
• Shear stress in a turbulent flow is a function of density - ρ.
• Transitional flow

5. CONTINUE…..
• Transitional flow is a mixture of laminar and turbulent flow, with turbulence in
the center of the pipe, and laminar flow near the edges. Each of these flows
behave in different manners in terms of their frictional energy loss while
flowing and have different equations that predict their behavior.
• Turbulent or laminar flow is determined by the dimensionless Reynolds Number.
• Reynolds Number
• The Reynolds number is important in analyzing any type of flow when there is
substantial velocity gradient (i.e. shear.) It indicates the relative significance of
the viscous effect compared to the inertia effect. The Reynolds number is
proportional to inertial force divided by viscous force.
• The flow is
• laminar when Re < 2300
• transient when 2300 < Re < 4000
• turbulent when 4000 < Re

6. TYPE OF FLOW
• Uniform Flow, Steady Flow
• It is possible - and useful - to classify the type of flow which is being examined into
small number of groups. If we look at a fluid flowing under normal circumstances - a
river for example - the conditions at one point will vary from those at another point
(e.g. different velocity) we have non-uniform flow. If the conditions at one point
vary as time passes then we have unsteady flow. Under some circumstances the flow
will not be as changeable as this. He following terms describe the states which are
used to classify fluid flow: •
• uniform flow: If the flow velocity is the same magnitude and direction at every
point in the fluid it is said to be uniform. •
• non-uniform: If at a given instant, the velocity is not the same at every point the
flow is non-uniform. (In practice, by this definition, every fluid that flows near a
solid boundary will be non-uniform - as the fluid at the boundary must take the
speed of the boundary, usually zero. However if the size and shape of the of the
cross-section of the stream of fluid is constant the flow is considered uniform.) •
• steady: A steady flow is one in which the conditions (velocity, pressure and cross-
section) may differ from point to point but DO NOT change with time. • unsteady: If
at any point in the fluid, the conditions change with time, the flow is described as
unsteady. (In practice there is always slight variations in velocity and pressure, but
if the average values are constant, the flow is considered steady.

7. CONTINUOUS
• Combining the above we can classify any flow in to one of four type:
• 1. Steady uniform flow. Conditions do not change with position in the
stream or with time. An example is the flow of water in a pipe of
constant diameter at constant velocity. Fluid Mechanics Fluid Dynamics:
The Momentum and Bernoulli Equations.
• 2. Steady non-uniform flow. Conditions change from point to point in the
stream but do not change with time. An example is flow in a tapering
pipe with constant velocity at the inlet - velocity will change as you
move along the length of the pipe toward the exit.
• 3. Unsteady uniform flow. At a given instant in time the conditions at
every point are the same, but will change with time. An example is a
pipe of constant diameter connected to a pump pumping at a constant
rate which is then switched off.
• 4. Unsteady non-uniform flow. Every condition of the flow may change
from point to point and with time at every point. For example waves in a
channel.

8. CONTINUOUS
• Compressible or Incompressible All fluids are compressible - even
water - their density will change as pressure changes. Under
steady conditions, and provided that the changes in pressure are
small, it is usually possible to simplify analysis of the flow by
assuming it is incompressible and has constant density. As you will
appreciate, liquids are quite difficult to compress - so under most
steady conditions they are treated as incompressible. In some
unsteady conditions very high pressure differences can occur and
it is necessary to take these into account - even for liquids.
Gasses, on the contrary, are very easily compressed, it is essential
in most cases to treat these as compressible, taking changes in
pressure into account.

9. continuous
• Three-dimensional flow Although in general all fluids flow three-
dimensionally, with pressures and velocities and other flow properties
varying in all directions, in many cases the greatest changes only occur
in two directions or even only in one. In these cases changes in the other
direction can be effectively ignored making analysis much more simple.
Flow is one dimensional if the flow parameters (such as velocity,
pressure, depth etc.) at a given instant in time only vary in the direction
of flow and not across the cross-section. The flow may be unsteady, in
this case the parameter vary in time but still not across the cross-
section. An example of one-dimensional flow is the flow in a pipe. Note
that since flow must be zero at the pipe wall - yet non-zero in the
Centre - there is a difference of parameters across the cross-section.
Should this be treated as two-dimensional flow? Possibly - but it is only
necessary if very high accuracy is required. A correction factor is then
usually applied.

10. continuous
• Flow is two-dimensional if it can be assumed that the flow parameters vary in
the direction of flow and in one direction at right angles to this direction.
Streamlines in two-dimensional flow are curved lines on a plane and are the
same on all parallel planes. An example is flow over a weir foe which typical
streamlines can be seen in the figure below. Over the majority of the length of
the weir the flow is the same - only at the two ends does it change slightly.
Here correction factors may be applied.
One
dimensional
flow

11. Two dimensional flow

12. Flow rate.
• Mass flow rate If we want to measure the rate at which water is flowing along
a pipe. A very simple way of doing this is to catch all the water coming out of
the pipe in a bucket over a fixed time period. Measuring the weight of the
water in the bucket and dividing this by the time taken to collect this water
gives a rate of accumulation of mass. This is know as the mass flow rate.
• Volume flow rate - Discharge. More commonly we need to know the volume
flow rate - this is more commonly know as discharge. (It is also commonly, but
inaccurately, simply called flow rate). The symbol normally used for discharge
is Q. The discharge is the volume of fluid flowing per unit time. Multiplying
this by the density of the fluid gives us the mass flow rate.

13. Type of flow measurement
•The most common principals for fluid flow
metering are:
•Differential Pressure Flow meters
•Velocity Flow meters
•Positive Displacement Flow meters
•Mass Flow meters
•Open Channel Flow meters

14. 1.Differential Pressure Flow meters
• In a differential pressure
drop device the flow is
calculated by measuring
the pressure drop over an
obstructions inserted in the
flow. The differential
pressure flow meter is
based on the Bernoulli's
Equation, where the
pressure drop and the
further measured signal is a
function of the square flow
speed.

15. • Common types of differential pressure flow meters are:
• Orifice Plates
• Flow Nozzles
• Venturi Tubes
• Variable Area - Rota meters
• Orifice Plate
An orifice plate is a device used for measuring flow rate, for
reducing pressure or for restricting flow (in the latter two
cases it is often called a restriction plate). Either a volumetric
or mass flow rate may be determined, depending on the
calculation associated with the orifice plate.With an orifice
plate, the fluid flow is measured through the difference in
pressure from the upstream side to the downstream side of a
partially obstructed pipe. The plate obstructing the flow offers
a precisely measured obstruction that narrows the pipe and
forces the flowing fluid to constrict.

16. continuous
• Orifice Plate is the heart of the Orifice Meter. It restricts
the flow and develops the Differential Pressure which is
proportional to the square of the flow rate. The flow
measuring accuracy entirely depends upon the quality of
Orifice plate, its installation and maintains.
• When measuring wet gas or saturated steam a weep hole
is drilled in a concentrically bored orifice plate. This is a
small hole drilled on the orifice plate such that its
location is exactly on ID of the main pipe.

17. • The Orifice plates are manufactured as per ISA / AGA/ API / ANSI
standards and in various materials
• such as SS304 /SS316 / SS316L /Hestoly C / Monel / PTFE coated.
• Various bores are used for various applications.
• Orifice Plate is categories in two types :- Paddle Type & Universal
Palate.
• Paddle Type Orifice Plate
• This plate is sandwiched between two Orifice Flanges. Tag Plate of
orifice plate projects out from Orifice flanges and it indicates the
existence of Orifice plate. Details such as Tag NO /Orifice ID / Pipe ID /
Plate Material are stamped on one side of the tag plate which faces
upstream side of the pipe line. Outside diameter of the orifice plate
equals to PCD-1 Bolt Dia. This ensures the concentricity with the main
pipe line. The other method to maintain the concentricity is by using
sleeves on the bolts or by providing dowel pins on the Orifice Flanges.
• Universal Orifice Plate
• This is a circular plate designed to fit in the Orifice fittings / Plate
holders / carrier rings / Ring Type Joints(RTJ).

18. Technical Specification
1.Size for Integral Design : 15, 20, 25, 40 mm
2.Size for Flanged Design : 25, 40, 50, 65, 80, 100, 150 ...250 mm
3.Material- Flanges & Carrier Ring : A105 / SS304/ SS316 / SS316L / CS & Other
materials on request.
4.Orifice Plate : SS304, SS316, SS316L, Hast C, Monel, PP, PVC,PTFE, Coated or
Clad with PP / HDPE / PTFE.
5.Gasket : CAF / SS Spiral Wound + CAF / PTFE / PVC / Rubber, Other materials
as per special request.
6.Stud / Nut : ASTM A193 Gr B/ASTM A194 CI 2H A193 B16/A194 C14
7.Standards Applicable : Design - ISA RP 3.2 / DN 1952 / BS 1042 - 1981-84
8.Bore Calculation : ISO 5167 / BS 1042 / RW Miller / L. K. SPIN / AGE - 3.7
9.Flanges : ANSI B-16-36 / or Equivalent
10.Types : Square edge concentric, Quadrant edges, Conical entrance,
Eccentric.
11.Pressure Toppings : For 1" to 16" - Flange Taps / Corner Taps. Above 16" - D x
D/2

19. Type Orifice Plate
• Paddle Type Orifice Plate
• Concentric Beveled Bore
Application :
This Most Common Bore Used In The
Industries. This Is The Only Type
Generally Accepted For Use In Custody
Transfer Measurement, Since Adequate
Data Is Not Available For Other Bores.
Used Primarily For Clean Homogeneous
Liquids, Gases, Non Viscous Fluids. The
Bevel Is Matched At 45° Angle To The
Desired Throat Thickness.

20. 2) Restriction Bore
Application :
This Type Is Not Used For
Flow Measurement But For
Dropping The Pressure
Considerably And Reducing
The Flow Accordingly. The
Bore Is Not Beveled But Kept
Straight. The Beta Ratio Has
No Limit As Accuracy Is Not
The Goal

21. Eccentric Bore
• Application :
Used For Measurement
Of Flow For Fluids
Containing Solids And
Slurries. It Is Also Used
For Vapors And Gases
Where Condensation Is
Present. The Eccentric
Bore Is Offset To Where
The Bore Edge Is
Inscribed In A Circle That
Is 98% The Line Id.

22. 4) Segmenta Bore
• Application :
• The Segmental Bore
Is Located In The
Same Way That The
Eccentric Bore Is.
This Type Is Used
Primarily For Slurries
Or Extremely Dirty
Gases Where The
Flow May Contain
Impurities Heavier
Than The Fluid.

23. Quadrant Bore
• Application :
Used For High Viscous
Fluids Such As Heavy
Crude, Syrups And
Slurries. It Is Always
Recommended For
Flow Where Reynolds
Number Is Less Than
10,000.The Inlet Is
Quarter Of A Circle And
The Plate Thickness
Must Be At Least
Radius Of The Inlet.

24. 6) Ring Type Joint –Integral
• Application :
• These Are
Available In
Oval Or Octal
Shapes.
Orifice Plate
Is A Part Of
RTJ Gasket.

25. Ring Type Joint- Separate
• Application :
These Are
Available In Oval
Or Octal Shapes.
The Orifice
Plate Is Universal
Type And Snap
Fitted On The
RTJ Gasket By
Screws.

26. Universal Orifice Plates
Application :
This Is A Circular Plate Designed To Fit In The
Orifice Fittings / Plate Holders / Carrier Rings /
Ring Type Joints(RTJ).

27. Various Orifice Assemblies
WNRF - Flange Taps WNRF - Corner Taps

28. Orifice working principle
Working:
§The orifice plate, being fixed at a section of the pipe,
creates an obstruction to the flow by providing an opening
in the form of an orifice to the flow passage.
When an orifice plate is placed in a pipe carrying the fluid
whose rate of flow is to be measured, the orifice plate
causes a pressure drop which varies with the flow rate.
This pressure drop is measured using a differential
pressure sensor and when calibrated this pressure drop
becomes a measure flow rate. The flow rate is given by.

29. Where, Qa = flow rate
Cd = Discharge coefficient
A1 = Cross sectional area of pipe
A2 = Cross sectional area of orifice
P1, P2 = Static Pressures
•The main parts of an orifice flow meter are as follows:
A stainless steel orifice plate which is held between flanges of a pipe carrying the fluid
whose flow rate is being measured.
•It should be noted that for a certain distance before and after the orifice plate fitted
between the flanges, the pipe carrying the fliud should be straight in order to maintain
laminar flow conditions.
•Openings are provided at two places 1 and 2 for attaching a differential pressure sensor
(U-tube manometer, differential pressure gauge etc) as shown in the diagram.

30. Operation of Orifice Meter
•
The detail of the fluid movement inside the pipe and orifice plate has to be
understood.
• The fluid having uniform cross section of flow converges into the orifice plate’s
opening in its upstream. When the fluid comes out of the orifice plate’s
opening, its cross section is minimum and uniform for a particular distance and
then the cross section of the fluid starts diverging in the down stream.
• At the upstream of the orifice, before the converging of the fluid takes place,
the pressure of he fluid (P1) is maximum. As the fluid starts converging, to
enter the orifice opening its pressure drops. When the fluid comes out of the
orifice opening, its pressure is minimum (p2) and this minimum pressure
remains constant in the minimum cross section area of fluid flow at the
downstream.
• This minimum cross sectional area of the fluid obtained at downstream from the
orifice edge is called VENA-CONTRACTA.
• The differential pressure sensor attached between points 1 and 2 records the
pressure difference (P1 – P2) between these two points which becomes an
indication of the flow rate of the fluid through the pipe when calibrated.

31. • Applications of Orifice Meter
•
The concentric orifice plate is used to measure flow rates of pure fluids and has a wide applicability as it has
been standardized.
• The eccentric and segmental orifice plates are used to measure flow rates of fluids containing suspended
materials such as solids, oil mixed with water and wet steam.
•
Advantages of Orifice Meter
•
It is very cheap and easy method to measure flow rate.
• It has predictable characteristics and occupies less space.
• Can be use to measure flow rates in large pipes.
•
Limitations of Orifice Meter
•
The vena-contracta length depends on the roughness of the inner wall of the pipe and sharpness of the orifice
plate. In certain cases it becomes difficult to tap the minimum pressure (P2) due to the above factor.
• Pressure recovery at downstream is poor, that is, overall loss varies from 40% to 90% of the differential
pressure.
• In the upstream straightening vanes are a must to obtain laminar flow conditions.
• Gets clogged when the suspended fluids flow.
• The orifice plate gets corroded and due to this after sometime, inaccuracy occurs. Moreover the orifice plate
has low physical strength.
• The coefficient of discharge is low.

32. Venturi Tube
• Due to simplicity and dependability, the Venturi tube flowmeter is
often used in applications where it's necessary with
higher TurnDown Rates, or lower pressure drops, than the orifice
plate can provide.
• In the Venturi Tube the fluid flow rate is measured by reducing the
cross sectional flow area in the flow path, generating a pressure
difference. After the constricted area, the fluid is passes through
a pressure recovery exit section, where up to 80% of the
differential pressure generated at the constricted area, is
recovered. With proper instrumentation and flow calibrating, the
Venturi Tube flowrate can be reduced to about 10% of its full scale
range with proper accuracy. This provides a TurnDown Rate 10:1.
•

33. Venturi tube

34. Flow Nozzles
• Flow nozzles
are often
used as
measuring
elements for
air and gas
flow in
industrial
applications

35. • The flow nozzle is relative simple and cheap, and available for
many applications in many materials.
• The Turndown Rate and accuracy can be compared with the orifice
plate.
• The Sonic Nozzle - Critical (Choked) Flow Nozzle
• When a gas accelerates through a nozzle, the velocity increase
and the pressure and the gas density decrease. The maximum
velocity is achieved at the throat, the minimum area, where it
breaks Mach 1 or sonic. At this point it's not possible to increase
the flow by lowering the downstream pressure. The flow is
choked.
• This situation is used in many control systems to maintain fixed,
accurate, repeatable gas flow rates unaffected by the downstream
pressure.

36. Recovery of Pressure Drop in Orifices, Nozzles
and Venturi Meters
• After the pressure difference
has been generated in the
differential pressure flow meter,
the fluid pass through the
pressure recovery exit section,
where the differential pressure
generated at the constricted
area is partly recovered. As we
can see, the pressure drop in
orifice plates are significant
higher than in the venturi tubes.

37. Variable Area Flow meter or Rota meter
• The Rota meter consists of
a vertically oriented glass
(or plastic) tube with a
larger end at the top, and
a metering float which is
free to move within the
tube. Fluid flow causes
the float to rise in the
tube as the upward
pressure differential and
buoyancy of the fluid
overcome the effect of
gravity.

38. continuous
• The float rises until the annular area between the float and tube
increases sufficiently to allow a state of dynamic equilibrium
between the upward differential pressure and buoyancy factors,
and downward gravity factors.
• The height of the float is an indication of the flow rate. The tube
can be calibrated and graduated in appropriate flow units.
• The rotameter meter typically have a TurnDown Ratio up to 12:1.
The accuracy may be as good as 1% of full scale rating.
• Magnetic floats can be used for alarm and signal transmission
functions.

39. Velocity Flow meters
• In a velocity flow meter the flow is calculated by measuring the
speed in one or more points in the flow, and integrating the flow
speed over the flow area

40. Pitot Tubes
• The pitot tube are one the
most used (and cheapest)
ways to measure fluid flow,
especially in air applications
like ventilation and HVAC
systems, even used in
airplanes for speed
measurent. The pitot tube
measures the fluid flow
velocity by converting the
kinetic energy of the flow
into potential energy.
• The use of the pitot tube is
restricted to point measuring.
With the "annubar", or multi-
orifice pitot probe, the
dynamic pressure can be
measured across the velocity
profile, and the annubar
obtains an averaging effect.
•

41. Calorimetric Flow meter
• The calorimetric principle for fluid flow measurement is based on
two temperature sensors in close contact with the fluid but
thermal insulated from each other.

42. One of the two sensors is constantly heated and the cooling effect of the flowing fluid is used to
monitor the flow rate. In a stationary (no flow) fluid condition there is a constant temperature
difference between the two temperature sensors. When the fluid flow increases, heat energy is
drawn from the heated sensor and the temperature difference between the sensors are reduced.
The reduction is proportional to the flow rate of the fluid.
Response times will vary due the thermal conductivity of the fluid. In general lower thermal
conductivity require higher velocity for proper measurement.
The calorimetric flow meter can achieve relatively high accuracy at low flow rates
Vortex Flow Meter
An obstruction in a fluid flow creates vortices in a downstream flow.
Every obstruction has a critical fluid flow speed at which vortex
shedding occurs. Vortex shedding is the instance where alternating
low pressure zones are generated in the downstream.

43. • Electromagnetic Flowmeter
• An electromagnetic flowmeter operate on Faraday's law of electromagnetic
induction that states that a voltage will be induced when a conductor moves
through a magnetic field. The liquid serves as the conductor and the magnetic
field is created by energized coils outside the flow tube.
• The voltage produced is directly proportional to the flow rate. Two electrodes
mounted in the pipe wall detect the voltage which is measured by a secondary
element.
• Electromagnetic flowmeters can measure difficult and corrosive liquids and
slurries, and they can measure flow in both directions with equal accuracy.
• Electromagnetic flowmeters have a relatively high power consumption and can
only be used for electrical conductive fluids as water.
• The Electromagnetic Flowmeter Principle - An introduction to the
electromagnetic flowmeter principle

44. Ultrasonic Doppler Flow meter
• The effect of motion of a sound source and its effect on the frequency
of the sound was observed and described by Christian Johann Doppler.
• The frequency of the reflected signal is modified by the velocity and
direction of the fluid flow
• If a fluid is moving towards a transducer, the frequency of the returning
signal will increase. As fluid moves away from a transducer, the
frequency of the returning signal decrease.
• The frequency difference is equal to the reflected frequency minus the
originating frequency and can be use to calculate the fluid flow speed.
• The Ultrasonic Doppler and Time of Flight Flow meter

45. Positive Displacement Flowmeter
•
• The positive displacement flow meter measures process fluid flow by precision-fitted rotors as flow
measuring elements. Known and fixed volumes are displaced between the rotors. The rotation of
the rotors are proportional to the volume of the fluid being displaced.
• The number of rotations of the rotor is counted by an integral electronic pulse transmitter and
converted to volume and flow rate.
• The positive displacement rotor construction can be done in several ways:
• Reciprocating piston meters are of single and multiple-piston types.
• Oval-gear meters have two rotating, oval-shaped gears with synchronized, close fitting teeth. A
fixed quantity of liquid passes through the meter for each revolution. Shaft rotation can be
monitored to obtain specific flow rates.
• Notating disk meters have movable disks mounted on a concentric sphere located in spherical side-
walled chambers. The pressure of the liquid passing through the measuring chamber causes the disk
to rock in a circulating path without rotating about its own axis. It is the only moving part in the
measuring chamber.
• Rotary vane meters consists of equally divided, rotating impellers, two or more compartments,
inside the meter's housings. The impellers are in continuous contact with the casing. A fixed volume
of liquid is swept to the meter's outlet from each compartment as the impeller rotates. The
revolutions of the impeller are counted and registered in volumetric units.
• The positive displacement flowmeter may be used for all relatively nonabrasive fluids such as
heating oils, lubrication oils, polymer additives, animal and vegetable fat, printing ink,
Dichlorodifluoromethane R-12, and many more.
• Accuracy may be up to 0.1% of full rate with a TurnDown of 70:1 or more.

46. Mass Flow meters
•
• Mass meters measure the mass flow rate directly.
• Thermal Flow meter
• The thermal mass flowmeter operates independent of density, pressure, and viscosity. Thermal
meters use a heated sensing element isolated from the fluid flow path where the flow stream
conducts heat from the sensing element. The conducted heat is directly proportional to the mass
flow rate and the temperature difference is calculated to mass flow.
• The accuracy of the thermal mass flow device depends on the calibrations reliability of the
actual process and variations in the temperature, pressure, flow rate, heat capacity and
viscosity of the fluid.
• Coriolis Flow meter
• Direct mass measurement sets Coriolis flowmeters apart from other technologies. Mass
measurement is not sensitive to changes in pressure, temperature, viscosity and density. With
the ability to measure liquids, slurries and gases, Coriolis flowmeters are universal meters.
• Coriolis Mass Flowmeter uses the Coriolis effect to measure the amount of mass moving through
the element. The fluid to be measured runs through a U-shaped tube that is caused to vibrate in
an angular harmonic oscillation. Due to the Coriolis forces, the tubes will deform and an
additional vibration component will be added to the oscillation. This additional component
causes a phase shift on some places of the tubes which can be measured with sensors.
• The Coriolis flow meters are in general very accurate, better than +/-0,1% with an turndown rate
more than 100:1. The Coriolis meter can also be used to measure the fluids density.

47. Open Channel Flow meters
• A common method of measuring
flow through an open channel is
to measure the height of the
liquid as it passes over an
obstruction as a flume or weir in
the channel.
• Common used is the Sharp-
Crested Weir, the V-Notch Weir,
the Cipolletti weir, the
Rectangular-Notch Weir, the
Parshall Flume or Venturi Flume.
•