Armfield C4-MKII User manual

An ISO 9001 Company
INSTRUCTION MANUAL
C4-MKII
ISSUE 7
SEPTEMBER 2006
MULTI-PURPOSE TEACHING FLUME

IMPORTANT SAFETY INFORMATION
All practical work areas and laboratories should be covered by local safety regulations which
must be followed at all times.
It is the responsibility of the owner to ensure that all users are made aware of relevant local
regulations, and that the apparatus is operated in accordance with those regulations. If requested
then Armfield can supply a typical set of standard laboratory safety rules, but these are guidelines
only and should be modified as required. Supervision of users should be provided whenever
appropriate.
Your Multi-Purpose Teaching Flume has been designed to be safe in use when installed,
operated and maintained in accordance with the instructions in this manual and with the
instructions in the product manual supplied with the F1-10 Hydraulics Bench. As with any piece
of sophisticated equipment, dangers may exist if the equipment is misused, mishandled or badly
maintained.
Electrical Safety
The equipment described in this Instruction Manual operates using a service unit (the F1-10
Hydraulics Bench) that is powered by a mains voltage electrical supply.
•The flume involves the use of water so any supply must be properly protected to
minimise the possibility of electric shock.
•The F1-10 Hydraulics Bench must be operated as described in the F1-10 product manual,
and must be tested regularly to ensure that the integral electrical protection is working
correctly.
Wet Environment
Use of the flume requires the presence of fast-moving water. During use it is probable that there
will be some spillage and splashing.
•All users should be made aware that they may be splashed while operating the equipment,
and should wear appropriate clothing and non-slip footwear.
•‘Wet Floor’ warnings should be displayed where appropriate.
•Electrical devices in the vicinity of the flume must be suitable for use in wet
environments or be properly protected from wetting.

Moving or Rotating Components
The C4-MKII Multi Purpose Teaching Flume has moving components.
•Before operating the jacking system ensure that no person or object can become trapped
by the movement of the flume or the jacking mechanism.
The C4-67 Wave Generator has moving and rotating components.
•Ensure that the Wave Generator has been securely fixed to the top of the inlet tank on the
flume before connecting the electrical supply.
•Do not remove any protective guards while the Wave Generator is in operation or
connected to the electrical supply.
•When operating the apparatus ensure that long hair is tied back out of the way, and that
clothing and jewellery cannot come into contact with any moving parts. Dangling items
such as necklaces or neckties must be removed or secured so that they cannot become
entangled in the equipment.
•Do not touch any moving components while the Wave Generator is in use, or insert any
item into any moving or rotating section of the equipment.
•Ensure that the apparatus is switched off and disconnected from the electrical supply
before handling the equipment or making adjustments to the stroke adjuster.
Heavy Equipment
This apparatus is heavy.
•The apparatus should be placed in a location that is sufficiently strong to support its
weight, as described in the Installation section of the manual.
•The support pedestals may be bolted to the floor for additional stability.
•The flume should be assembled in place whenever possible. Where manual lifting is
necessary, two or more people will be required for safety. All should be made aware of
safe lifting techniques to avoid injury.
•Safety shoes and/or gloves should be worn when appropriate when moving the
equipment.
•If the apparatus is to be repositioned after installation, the apparatus must be drained
before it is moved and should be disassembled if possible.

Water Borne Hazards
The equipment described in this instruction manual involves the use of water, which under
certain conditions can create a health hazard due to infection by harmful micro-organisms.
For example, the microscopic bacterium called Legionella pneumophila will feed on any scale,
rust, algae or sludge in water and will breed rapidly if the temperature of water is between 20 and
45°C. Any water containing this bacterium which is sprayed or splashed creating air-borne
droplets can produce a form of pneumonia called Legionnaires Disease which is potentially fatal.
Legionella is not the only harmful micro-organism which can infect water, but it serves as a
useful example of the need for cleanliness.
Under the COSHH regulations, the following precautions must be observed:-
•Any water contained within the product must not be allowed to stagnate, i.e. the water
must be changed regularly.
•Any rust, sludge, scale or algae on which micro-organisms can feed must be removed
regularly, i.e. the equipment must be cleaned regularly.
•Where practicable the water should be maintained at a temperature below 20°C. If this is
not practicable then the water should be disinfected if it is safe and appropriate to do so.
Note that other hazards may exist in the handling of biocides used to disinfect the water.
•A scheme should be prepared for preventing or controlling the risk incorporating all of
the actions listed above.
Further details on preventing infection are contained in the publication “The Control of
Legionellosis including Legionnaires Disease” - Health and Safety Series booklet HS (G) 70.

MULTI-PURPOSE TEACHING FLUME
C4-MKII
Contents
1Introduction to the Equipment ......................................................................................................................... 7
1.1 Diagram 1: Inlet End of Flume .................................................................................................................. 8
1.2 Diagram 2: Discharge End of Flume......................................................................................................... 9
2Description........................................................................................................................................................ 10
2.1 Overview .................................................................................................................................................. 10
2.2 Working Section ....................................................................................................................................... 10
2.3 Inlet Tank ................................................................................................................................................. 10
2.4 Overshot Weir .......................................................................................................................................... 10
2.5 Optional Flowmeter ................................................................................................................................. 10
2.6 Hook and Point Gauges ........................................................................................................................... 11
2.7 Pedestals and Jack ................................................................................................................................... 11
2.8 The F1-10 Hydraulics Bench ................................................................................................................... 11
3Operation.......................................................................................................................................................... 13
3.1 Positioning the F1-10 Hydraulics Bench ................................................................................................. 13
3.2 Connecting the F1-10 Hydraulics Bench................................................................................................. 13
3.3 Filling the F1-10 Hydraulics Bench with water....................................................................................... 14
3.4 Assembling and Installing Models ...........................................................................................................14
3.5 Assembling and Installing the Venturi Flume .......................................................................................... 15
3.6 Installing the Optional False Floor Sections ........................................................................................... 15
3.7 Installing the Optional Roughened Bed Sections..................................................................................... 16
3.8 Sealing models into the flume................................................................................................................... 16
3.9 Use of Stop Logs to Vary Flume Flow Depth........................................................................................... 16
3.10 Installing the Optional Pitot Tube and Manometer Board (C4-61) ......................................................... 17
3.11 Operating the Optional Pitot Tube and Manometer (C4-61)................................................................... 18
3.12 Installing the Optional Wave Generator (C4-67)..................................................................................... 20
3.13 Operating the Optional Wave Generator (C4-67) ................................................................................... 20

4Specifications....................................................................................................................................................22
4.1 Overall Dimensions..................................................................................................................................22
4.2 Working Section Dimensions....................................................................................................................22
4.3 Flume Slope.............................................................................................................................................. 22
4.4 Flow Rate ................................................................................................................................................. 22
4.5 Electrical Supply ......................................................................................................................................23
4.6 Water Supply and Drain...........................................................................................................................23
4.7 Hook and Point Gauges (2 supplied) .......................................................................................................23
4.8 Models Available for Use in the C4-MkII Flume .....................................................................................23
5Routine Maintenance.......................................................................................................................................25
5.1 General..................................................................................................................................................... 25
5.2 RCD test for F1-10 Hydraulics Bench ..................................................................................................... 25
5.3 Test condition of water in F1-10 Hydraulics Bench.................................................................................25
5.4 Check C4-MkII for leaks ..........................................................................................................................25
5.5 Check condition of channel bed ............................................................................................................... 26
5.6 Full annual service...................................................................................................................................26
6Laboratory Teaching Exercises ......................................................................................................................29
6.1 Index to Exercises.....................................................................................................................................29
6.2 General Nomenclature .............................................................................................................................30
6.3 Nomenclature for Free Surface Flow.......................................................................................................31
6.4 Exercise A: Sharp Crested Overshot Weir ............................................................................................... 32
6.5 Exercise B: Broad Crested Weir ..............................................................................................................36
6.6 Exercise C: Crump Weir...........................................................................................................................40
6.7 Exercise D: Discharge Beneath a Sluice Gate.........................................................................................44
6.8 Exercise E: Force on a Sluice Gate .........................................................................................................48
6.9 Exercise F: The Specific Energy Equation...............................................................................................52
6.10 Exercise G: The Hydraulic Jump .............................................................................................................57
6.11 Exercise H: Flow Through a Venturi Flume ............................................................................................ 61
6.12 Exercise J: Flow Through a Culvert ........................................................................................................ 65
6.13 Exercise K: Flow Around Flow Splitters.................................................................................................. 68
6.14 Exercise L: Flow Over a Dam Spillway ...................................................................................................71
6.15 Exercise M: Flow Through a Siphon Spillway.........................................................................................74
6.16 Exercise N: Flow Through an Air Regulated Siphon ...............................................................................78
6.17 Exercise P: Flow Under a Radial Gate....................................................................................................84
6.18 Exercise Q: Flow Over False Floor Sections...........................................................................................87
6.19 Exercise R: Flow Over a Gravel Bed .......................................................................................................90
7Installation Guide................................................................................................................................................i

7
1 Introduction to the Equipment
When studying Hydraulics, the fundamental concepts of energy and momentum are sometimes
difficult to grasp, particularly where free surface flow is concerned. The Armfield Multi-Purpose
Teaching Flume has been developed to assist the student to overcome this difficulty. It provides a
basic but nonetheless comprehensive facility for student experiments in open channel flow.
Although small in comparison with the majority of flumes, the dimensions of the working
section have been sized so that the various phenomena may be clearly seen and reasonably
accurate results may be obtained from measurements taken.
The C4-MkII flume is supplied with either a 2.5 metre long working section or a 5.0 metre long
working section. Both versions of the flume can be fitted with an optional direct reading
flowmeter for convenience in operation. A set of basic models is included with all versions of the
flume. A range of optional models is also available to extend the experimental capabilities.
This manual covers all versions of the C4-MkII flume.
The flume requires the use of a standard Armfield Hydraulics Bench F1-10 (ordered
separately) which stores water for recirculation making the unit self contained, except for the
provision of an electrical supply. The construction of the flume allows for easy disassembly if at
a later date it is required to move the unit to a different location.
This manual includes experimental sheets detailing some of the demonstrations and exercises
which can be performed using the flume and models. We wish to emphasise that these
experiments do not exhaust the potential of the flume or the models. There are many further
investigations that an imaginative user can devise and the user can construct alternative models
for installation in the flume.
C4-MkII Multi-Purpose Teaching Flume
Shown with F1-10 Hydraulics Bench and optional flowmeter

8
1.1 Diagram 1: Inlet End of Flume
1
2
3
5
6
8
7
4

9
1.2 Diagram 2: Discharge End of Flume
10
3
1
8
2
7
9
11

10
2 Description
Numerical references refer to the drawings on pages 8 and 9.
2.1 Overview
The flume consists of a clear-sided rectangular working section supported on a frame,
with an inlet tank at one end. The frame is supported on pedestals, and a jack allows the
flume to be tilted. The flume is designed to be used with an Armfield F1-10 Hydraulics
Bench, which provides a re-circulating water supply and a volumetric measuring facility.
2.2 Working Section
The working section of the channel (1), which is open at the top, consists of clear acrylic
sides which are sealed to a bed (8) fabricated from painted aluminium alloy. The clear
sides allow full visualisation of the flow conditions inside the working section. Spacers
(3) across the top edges of the sides ensure that the flume sides remain rigid. The bed of
the working section incorporates pressure tappings with isolating valves and model
mounting points (See section 3.2 for further information). Two carriers (2), mounted
across the top edges of the channel walls, allow hook and point level gauges to be used to
measure the depth of water at any position along the length of the working section. See
section 2.6.
2.3 Inlet Tank
Water enters the parallel working section via the inlet tank (4) that is constructed from
PVC. The water pipe entering the inlet tank has diffused outlets and the water flows
through a diffuser and a perforated plate to reduce any turbulence in the water and
produce a smooth flow of water into the working section of the channel.
2.4 Overshot Weir
The level in the working section of the flume may be controlled by an overshot weir
arrangement at the exit (10) consisting of stop logs in a slot. Stop logs are simply added
or taken away to provide the required depth of water in the working section. Water
exiting from the channel discharges into the moulded channel on top of the F1-10
Hydraulics Bench (11) where it returns by gravity to the sump tank via the volumetric
measuring tank.
2.5 Optional Flowmeter
An optional shunt type flowmeter (9) can be supplied with the flume to provide a direct
reading of the volume flowrate of the water passing through the working section of the
flume. This provides a convenient means of setting up the various open channel
demonstrations without the need for repeated timings using a stopwatch. When supplied
this flowmeter is mounted on the pivot pedestal of the flume and consists of a variable

11
area flowmeter which is shunted across an orifice plate with the scale calibrated to read
the actual flow.
When the flowmeter is not fitted (or at low flowrate below 1.2 litres/second) the flowrate
can be measured using the volumetric tank on the F1-10 Hydraulics Bench
2.6 Hook and Point Gauges
A pair of hook and point gauges enable the height of the water above the bed to be
measured at two different locations. The gauges can be located along the length of the
channel on carriers (2) that are located on top of the channel sides. A measuring scale
attached along the top of the front channel side indicates the position of each gauge along
the length of the channel. The gauges incorporate a scale with Vernier and a fine adjusting
screw that allow accurate measurement of the water depth. Either the hook or the point
may be clamped to the end of the vertical mast of the gauge to suit the operator – the
point is used by observing the reflection on the surface of the water, the hook is used by
observing the reflection through the water. The hook or point is correctly positioned when
the tip and its reflection just touch. Measurements will not be accurate when a meniscus
forms between the water surface and the tip.
2.7 Pedestals and Jack
The flume is supported on a pair of pedestals (7) which should be bolted to the floor for
additional safety. The pedestal at the inlet end of the working section is fitted with a
hand-operated jack. This jacking arrangement permits the slope of the channel bed to be
manually adjusted. The jack is operated by a handwheel (5) and the mechanism
incorporates a slope indicator (6) calibrated directly in units of % slope. For normal
operation the slope should be set to 0% (bed of channel level).
2.8 The F1-10 Hydraulics Bench
The C4-MkII is designed for use with the F1-10 Hydraulics Bench. The F1-10 is not
supplied as part of C4-MkII.
Water is drawn from a sump tank in the base of the F1-10 by a centrifugal pump. The
water is delivered to the inlet tank of the flume via a flexible tube that is connected to the
outlet in the moulded channel on the top of the F1-10. The flow of water through the
working section is varied using the flow control valve on the side of the F1-10 Hydraulics
Bench.
Having flowed along the working section of the flume the water falls by gravity into the
moulded channel on the top of the F1-10. The water then flows into a volumetric tank
before returning to the sump tank under gravity. The volumetric tank provides a means
(and demonstration) of measuring the flow of water through the flume when not using the
optional direct reading flowmeter.
Flowrates up to approximately 1.2 litre/sec can be measured using the volumetric tank
and a stopwatch (not supplied). In normal operation the dump valve in the base of the
volumetric tank should be open to allow the water to re-circulate. When measuring the
flowrate the dump valve is dropped into the aperture and the flow is measured by timed

12
volume collection. Using the sight glass (level scale) on the side of the F1-10 and a
stopwatch.
At higher flowrate (above 1.2 litres/sec) it will be necessary to use the circular orifice
plate supplied with the C4-MkII to measure the flowrate as the volumetric tank will
remain flooded. To install the orifice plate lift the ball and weight from the aperture in the
base of the volumetric tank then press the orifice plate into the aperture. At each flow
setting allow the water level to stabilise in the volumetric tank (this may take several
minutes after making a change in flowrate) then read the value from the upper scale on
the F1-10 sight glass (level gauge). This reading in litres is used to find the actual flow
rate by referring to the following table:
Flow Rate Reference Table (Only used with C4-MKII up to 1.6 l/s)
Scale Reading
Litres
Flow Rate
Litres/sec
Scale Reading
Litres
Flow rate
Litres/sec
0 1.41 12 1.78
1 1.44 13 1.81
2 1.48 14 1.84
3 1.51 15 1.86
4 1.54 16 1.89
5 1.57 17 1.92
6 1.60 18 1.94
7 1.63 19 1.97
8 1.66 20 2.00
9 1.69 21 2.02
10 1.72 22 2.05
11 1.75 23 2.07
Note that when using the C4-MKII Tilting Flume in conjunction with the F1-10
Hydraulics Bench the maximum flowrate available is approximately 1.6 litres/sec (approx
96 litres/min).
Additional information about the F1-10 Hydraulics Bench is provided in the separate
product manual supplied with the F1-10. Refer to that manual for full information
including installation and commissioning instructions.

13
3 Operation
Where necessary, refer to the drawings on pages 8 and 9.
3.1 Positioning the F1-10 Hydraulics Bench
The C4-MkII is designed for use with the F1-10 Hydraulics Bench. The flume discharges
into the horizontal channel that is moulded into the top of the F1-10. The F1-10 must
therefore be positioned to allow water discharging from the flume to enter the top channel
with minimal splashing. Water should enter the channel just beyond the lip of the channel,
without hitting the lip, remaining clear of the end wall of the channel, as shown:
As the flow rate and flume slope is altered, the angle of the water exiting the flume will
change slightly. It may be necessary to move the F1-10 to allow for this, ensuring that the
discharge flow always enters the channel centrally to prevent splashing on the sides of the
channel. The F1-10 Hydraulics Bench is mounted on casters for ease of repositioning.
3.2 Connecting the F1-10 Hydraulics Bench
Disconnect any accessory that is already connected to the quick release connector on the
F1-10 (connector located inside the top moulded channel on the F1-10). Ensure that the F1-
10 is switched off and the flow control valve is closed then unscrew the quick release
connector from the bed of the channel. Screw the adaptor, supplied with C4-MkII, onto the
threaded outlet in the bed of the channel then connect the flexible tube from the C4-MkII to
the union on top of the adaptor. The union incorporates a ‘O’ ring seal and only needs to be
hand tight (do not use a tool to tighten the fitting).
To restore the F1-10 to normal use; unscrew the union to disconnect the flexible tube then
unscrew the adaptor from the threaded outlet in the bed of the channel on F1-10. Screw the
quick release connector onto the threaded outlet to allow the F1-10 to be used with any
other accessories. It may be necessary to move the F1-10 slightly to the left to allow
operation with some accessories but the castors on the F1-10 allow the unit to be easily
repositioned.

14
3.3 Filling the F1-10 Hydraulics Bench with water
Place a filling hose in the volumetric tank of the F1-10. Fill the sump tank with clean cold
water by lifting the dump valve in the base of the volumetric measuring tank and allowing
the water to drain from the volumetric tank into the sump tank. (When lifted, a twist of 90°
at the actuator will retain the dump valve in the open position.) When full ensure that the
water level in the sump tank is just level with the outlet in the bottom of the volumetric
tank.
A few drops of wetting agent (Teepol or similar) should be added to the water in the sump
tank to reduce the effect of surface tension. Note that too much wetting agent will cause
foaming.
3.4 Assembling and Installing Models
The bed-mounted models (with the exception of the Venturi flume, the false floor sections
and the artificially roughened bed as described in later sections) are hooked in place via a
retaining bar on the underside of the model using a clamping hook assembly. The rod
incorporating the hook passes through a gland on the underside of the channel bed that
incorporates a rubber ‘O’ ring seal to prevent water from leaking. Each gland should be
adjusted so that the rod will move smoothly when pushed up or down but remain in
position without leaking.
There are two hooks per 2.5 metre length of channel section. The diagrams below show
how the model is retained in position. The appropriate hook is pushed upwards to clear the
channel bed. The required model is placed over the hook and then slid along until its
retaining bar is beneath the hook. The hook is then pulled downwards from beneath to
secure the model. The model will be held in place until the hook is pushed up again.

15
When not in use the model clamping rods can be inverted to minimise disturbance to the
flow along the bed of the channel. To invert the rod unscrew the gland on the underside of
the bed then pull the rod out from the gland from above. Re-insert the rod into the gland
from below (taking care not to damage the ‘O’ ring in the gland) with the tip of the rod
flush with the channel bed. Tighten the gland to retain the rod in position.
3.5 Assembling and Installing the Venturi Flume
The Venturi flume is held in place by a simple stretcher screw. This is placed between the
two sections of the Venturi and adjusted to clamp them against the side walls of the
channel.
NOTE: The stretcher must be placed above the level of the water so as not to interfere with
the flow:
3.6 Installing the Optional False Floor Sections
The false floor sections are secured with the use of holes in the bed floor. The hooks are
removed from the holes and pins are used instead. Each section of floor uses two pins
which push through the floor section and into the two holes in each working section (one
section if 2.5m, two sections if 5m). The end ramps simply slot into the required end of the
floor. The raised floor support is held in compression between the floor and the channel
bed.

16
3.7 Installing the Optional Roughened Bed Sections
The artificially roughened (gravel) bed relies on its own weight to hold it onto the channel
bed. It is aided by a bed end stop which is similar to the stretcher screw used on the Venturi
flume except that it clamps between the channel side walls. This acts as a stop which
prevents the gravel bed from sliding along the channel bed.
3.8 Sealing models into the flume
Plasticine is supplied with the flumes. This is used on the leading edge of the model and is
placed between the side walls and bed of the channel and the sides of the model. This is to
ensure that water flows over the model and not around or under it.
3.9 Use of Stop Logs to Vary Flume Flow Depth
The stop logs supplied slot into the discharge end of the channel. They may be used singly
and in combination to raise the water level within the flume to different heights. Gaps
between the logs may be sealed with Plasticine if required, but this is not usually necessary.

17
3.10 Installing the Optional Pitot Tube and Manometer Board (C4-61)
The Pitot tube and manometer board is an optional accessory (Armfield order code C4-61)
and is used in conjunction with the C4-MkII Multi Purpose Teaching Flume to measure the
local velocity of water flowing through the working section.
Partially fill the flume with water so that the head of the Pitot tube can be immersed when
installed on the flume. The water in the flume should not be flowing during the priming
procedure.
Before installing the Pitot tube and manometer on the flume it is necessary to prime them
with water. Fill the manometer reservoir with water, ensuring that the valve at the base of
the reservoir is closed. Position the manometer above the Pitot tube with the Pitot tube
sloping uphill (cranked head at the top). Open the isolating valves at the base of the
manometer.
Open the reservoir and allow water to flow through the flexible tubing until it flows
through the static and total head holes in the Pitot tube. During this operation the reservoir
must not be allowed to empty, thus letting air into the system. Ensure that there are no air
bubbles in the assembly. Close the valve at the base of the reservoir on the manometer.
Set up the Pitot tube as shown in the diagram above with the head of the tube immersed
under water. Ensure that the reservoir on the manometer is filled with water with the valve
closed. Raise the manometer above the flume then open the valve and allow water to flow
through the assembly. Ensure that no air remains in the pipework. Briefly raise the head of
the Pitot tube above the level of the water in the flume and check that water flows from
both the static and total head holes. Once again the reservoir on the manometer must not be
allowed to empty during the priming operation.
If any air is trapped in the pipework the whole of the procedure should be repeated. It is
essential that no air is present, otherwise reading obtained will be valueless.
Flexible Tubes Level Gauge
Reservoir
Pitot Static Tube
Valve
500mm manometer
paraffin / water

18
Allow water to drain from the reservoir leaving a small amount in the base, then close the
isolating valves at the base of the manometer. Fill the reservoir with paraffin (Kerosene,
Specific Gravity = 0.784) then open each isolating valve in turn to half fill each manometer
tube with paraffin. Take care to avoid slugs of paraffin/water in the manometer tubes.
When both tubes are correctly filled to mid height close the isolating valve at the base of
the reservoir.
Close the isolating valves at the base of the manometer until the equipment is ready for
use.
3.11 Operating the Optional Pitot Tube and Manometer (C4-61)
The Pitot tube and manometer are used for measuring low velocities of water in the flume.
If used with excessively high velocities, the paraffin will be pushed out of the manometer
into the flexible tubing which may result in paraffin entering the flume.
DO NOT open the valve at the base of the reservoir during operation.
Open the flume inlet valve and allow water to flow slowly through the flume. Carefully
open the isolating valves at the base of the manometer and note the difference in levels in
the two limbs of the manometer.
The velocity of the water is calculated as follows:
For the Pitot tube
(
)
f
st
ρ
pp2
kv − =
For the manometer (pt- ps) = g h (ρf- ρm)
where:
v = Local velocity of water (m s-1)
k = Pitot tube coefficient (can be assumed to be unity) (Dimensionless)
pt= Total pressure (N m-2)
ps= Static pressure (N m-2)
ρf= Density of operating fluid, water (kg m-3)
ρm= Density of manometer fluid, paraffin (kg m-3)
h = Difference in levels in manometer (m)
g = Gravitational constant (9.81m s-2)
therefore:
v =
(
)
1000
7841000gh2 −
v = h24.4 (m s-1)